Spectroscopy: Difference between revisions

Latest revision as of 13:55, 31 December 2025

File:Light dispersion of a mercury-vapor lamp with a flint glass prism IPNr°0125.jpg

A prism separates white light by dispersing it into its component colors, which can then be studied using spectroscopy.

Spectroscopy is the field of study that measures and interprets electromagnetic spectra as it interacts with matter.^[1] In narrower contexts, spectroscopy is the precise study of color as generalized from radiated visible light to all bands of the electromagnetic spectrum.

Spectroscopy, primarily in the electromagnetic spectrum, is a fundamental exploratory tool in the fields of astronomy, chemistry, materials science, and physics, allowing the composition, physical and electronic structure of matter to be investigated at the atomic, molecular and macro scale, and over astronomical distances.

Historically, spectroscopy originated as the study of the wavelength dependence of the absorption by gas phase matter of visible light dispersed by a prism. Current applications of spectroscopy include biomedical spectroscopy in the areas of tissue analysis and medical imaging. Matter waves and acoustic waves can be considered forms of radiative energy, and recently gravitational waves have been associated with a spectral signature in the context of the Laser Interferometer Gravitational-Wave Observatory (LIGO).^[2]

Introduction

Spectroscopy is a branch of science concerned with the spectra of electromagnetic radiation as a function of its wavelength or frequency, as measured by spectrographic equipment and other techniques, in order to obtain information concerning the structure and properties of matter.^[3] Spectral measurement devices are referred to as spectrometers, spectrophotometers, spectrographs or spectral analyzers. Most spectroscopic analysis in the laboratory starts with a sample to be analyzed. A light source is sent through a monochromator to spatially separate the colors before passing a selected frequency band through the sample, then the output is captured by a photodiode.^[4] For astronomical purposes, the telescope must be equipped with the light dispersion device.^[5] There are various versions of this basic setup that may be employed.

File:High resolution solar spectrum (noao-sun).jpg

High resolution spectrum of the Sun, showing the discrete line pattern created by elements in the stellar atmosphere

Spectroscopy began with Isaac Newton splitting light with a prism; a key moment in the development of modern optics.^[6] Therefore, it was originally the study of visible light that we call color. Following the contributions of James Clerk Maxwell, this study later came to include the entire electromagnetic spectrum.^[7] Although color is involved in spectroscopy, it is not equivalent to the absorption and reflection of certain electromagnetic waves that give objects or elements a sense of color to our eyes. Rather, spectroscopy involves the splitting of light by a prism, diffraction grating, or similar instrument, to display a particular discrete line pattern called a "spectrum", which is unique for each different type of element or molecule. Most elements are first put into a gaseous state to allow the spectra to be examined, although today other methods can be used for different phases of matter. Each element that is diffracted by a prism-like instrument displays either an absorption spectrum or an emission spectrum depending upon whether the element is being cooled or heated.^[8]

Until recently all spectroscopy involved the study of line spectra and most spectroscopy still does.^[9] Vibrational spectroscopy is the branch of spectroscopy that studies the spectra.^[10] However, the latest developments in spectroscopy can sometimes dispense with the dispersion technique. In biochemical spectroscopy, information can be gathered about biological tissue by absorption and light scattering techniques. Light scattering spectroscopy is a type of reflectance spectroscopy that determines tissue structures by examining elastic scattering.^[11] In such a case, it is the tissue that acts as a diffraction or dispersion mechanism.

Spectroscopic studies were central to the development of quantum mechanics. The first useful quantum atomic models, including Bohr model, the Schrödinger equation, and Matrix mechanics, reproduced the spectral lines of hydrogen. These equated discrete quantum jumps of the bound electron in a hydrogen atom to the discrete hydrogen spectrum. Max Planck's explanation of blackbody radiation involved spectroscopy because he was comparing the wavelength of light using a photometer to the temperature of a Black Body.^[12] Spectroscopy is used in physical and analytical chemistry because atoms and molecules have unique spectra. As a result, these spectra can be used to detect, identify and quantify information about the atoms and molecules.

Spectroscopy is used in astronomy and remote sensing on Earth. Most research telescopes have spectrographs. The measured spectra are used to determine the chemical composition and physical properties of astronomical objects, such as their temperature, elemental abundances, velocity, rotation, magnetic field, and more.^[13] An important use for spectroscopy is in biochemistry. Molecular samples may be analyzed for species identification and energy content.^[14]

Theory

The underlying premise of spectroscopy is that light is made of different wavelengths and that each wavelength corresponds to a different frequency. The importance of spectroscopy is centered around the fact that every element in the periodic table has a unique light spectrum described by the frequencies of light it emits or absorbs consistently appearing in the same part of the electromagnetic spectrum when that light is diffracted.^[15] This opened up an entire field of study with anything that contains atoms. Spectroscopy is the key to understanding the atomic properties of all matter. As such spectroscopy opened up many new sub-fields of science yet undiscovered. The idea that each atomic element has its unique spectral signature enabled spectroscopy to be used in a broad number of fields each with a specific goal achieved by different spectroscopic procedures. The National Institute of Standards and Technology maintains a public Atomic Spectra Database that is continually updated with precise measurements.^[16]

With an absorption spectrophotometer, the level of absorption of a light source is determined by the Beer-Lambert Law: $\ln (\frac{I_{0}}{I}) = ε ℓ c$ where $I_{0}$ is the light intensity before passing through the sample, $I$ is the output intensity, $ε$ is the extinction coefficient, $ℓ$ is the path length through the sample, and $c$ is the concentration of the sample. The extinction coefficient depends on the wavelength selected and the molecule being sampled.^[4]

Resonances by the frequency were first characterized in mechanical systems such as pendulums, which have a frequency of motion noted famously by Galileo.^[17] In quantum mechanical systems, the analogous resonance is a coupling of two quantum mechanical stationary states of a system, such as two atomic orbitals, via an oscillatory source of energy such as a photon. The coupling of the two states is strongest when the source energy matches the energy difference between the two states.Script error: No such module "Unsubst". That is, a photon at the right energy is more likely to cause an electron to jump between two orbitals, a process called electron excitation. The energy Template:Mvar of a photon is related to its frequency Template:Mvar by $E = hν$ Script error: No such module "Check for unknown parameters". where Template:Mvar is the Planck constant,^[18] and so a spectrum of the system response vs. photon frequency will peak at the resonant frequency or energy.

Any part of the electromagnetic spectrum may be used to analyze a sample from the infrared to the ultraviolet telling scientists different properties about the very same sample, a discovery that led to a broadening of the field of spectroscopy. For instance in chemical analysis, the most common types of spectroscopy include atomic spectroscopy, infrared spectroscopy, ultraviolet and visible spectroscopy, Raman spectroscopy and nuclear magnetic resonance.^[19] In nuclear magnetic resonance (NMR), the theory behind it is that frequency is analogous to resonance and its corresponding resonant frequency.

Classification of methods

File:A Taste of ESPRESSO.jpg

A huge diffraction grating at the heart of the ultra-precise ESPRESSO spectrograph.^[20]

Spectroscopy is a sufficiently broad field that many sub-disciplines exist, each with numerous implementations of specific spectroscopic techniques. The various implementations and techniques can be classified in several ways.

Type of radiative energy

The types of spectroscopy are distinguished by the type of radiative energy involved in the interaction. In many applications, the spectrum is determined by measuring changes in the intensity or frequency of this energy. The types of radiative energy studied include:

Electromagnetic radiation was the first source of energy used for spectroscopic studies. Techniques that employ electromagnetic radiation are typically classified by the wavelength region of the spectrum and include microwave,^[21] terahertz,^[22] infrared,^[23] near-infrared,^[24] ultraviolet-visible,^[25] X-ray,^[26] and gamma spectroscopy.^[27]
Particles, because of their de Broglie waves, can be a source of radiative energy.^[28] Both electron^[29] and neutron spectroscopy are used.^[26] For a particle, its kinetic energy determines its wavelength.^[28]
Acoustic spectroscopy involves radiated pressure waves.^[30]
Dynamic mechanical analysis can be employed to impart radiating energy, similar to acoustic waves, to solid materials.^[31]

Nature of the interaction

The types of spectroscopy can be distinguished by the nature of the interaction between the energy and the material. These interactions include:^[32]

Absorption spectroscopy: Absorption occurs when energy from the radiative source is absorbed by the material. Absorption is often determined by measuring the fraction of energy transmitted through the material, with absorption decreasing the transmitted portion.
Emission spectroscopy: Emission indicates that radiative energy is released by the material. A material's blackbody spectrum is a spontaneous emission spectrum determined by its temperature. This feature can be measured in the infrared by instruments such as the atmospheric emitted radiance interferometer.^[33] Emission can be induced by other sources of energy such as flames, sparks, electric arcs or electromagnetic radiation in the case of fluorescence.
Elastic scattering and reflection spectroscopy determine how incident radiation is reflected or scattered by a material. Crystallography employs the scattering of high energy radiation, such as X-rays and electrons, to examine the arrangement of atoms in proteins and solid crystals.
Impedance spectroscopy, where impedance is the ability of a medium to impede or slow the transmittance of energy. For optical applications, this is characterized by the index of refraction.
Inelastic scattering phenomena involve an exchange of energy between X-ray radiation and the matter that shifts the wavelength of the scattered radiation. These include Raman and Compton scattering.^[34]
Coherent or resonance spectroscopy are techniques where the radiative energy couples two quantum states of the material in a coherent interaction that is sustained by the radiating field. The coherence can be disrupted by other interactions, such as particle collisions and energy transfer, and so often requires high intensity radiation to be sustained. Nuclear magnetic resonance (NMR) spectroscopy is a widely used resonance method, and ultrafast laser spectroscopy is possible in the infrared and visible spectral regions.
Nuclear spectroscopy are methods that use the properties of specific nuclei to probe the local structure in matter, mainly condensed matter, molecules in liquids or frozen liquids and bio-molecules.
Quantum logic spectroscopy is a general technique used in ion traps that enables precision spectroscopy of ions with internal structures that preclude laser cooling, state manipulation, and detection. Quantum logic operations enable a controllable ion to exchange information with a co-trapped ion that has a complex or unknown electronic structure.

Type of material

Spectroscopic studies are designed so that the radiant energy interacts with specific types of matter. These studies can be divided into three broad categories:^[35] electronic spectroscopy, which measures the transition of electrons between different energy states through absorption or emission of visible or ultraviolet energy; vibronic spectroscopy of molecules induced by the absorption of infrared energy; and rotational spectroscopy of molecules caused by microwave energy.^[36] The last two can be combined into rotational–vibrational spectroscopy of a gas.

Atoms

File:Welsbach Figure IV spektroskopische-lytischen-chemie-21.pdf

Atomic spectra comparison table, from "Spektroskopische Methoden der analytischen Chemie" (1922).

Atomic spectroscopy was the first application of spectroscopy. Atomic absorption spectroscopy and atomic emission spectroscopy involve visible and ultraviolet light. These absorptions and emissions, often referred to as atomic spectral lines, are due to electronic transitions of outer shell electrons as they rise and fall from one electron orbit to another. Atoms have distinct X-ray spectra that are attributable to the excitation of inner shell electrons to excited states.

Atoms of different elements have distinct spectra and therefore atomic spectroscopy allows for the identification and quantitation of a sample's elemental composition. After Robert Bunsen and Gustav Kirchhoff invented the spectroscope, Bunsen discovered cesium and rubidium by observing their emission spectra.^[37] Atomic absorption lines are observed in the solar spectrum and referred to as Fraunhofer lines after their discoverer.^[38] A comprehensive explanation of the hydrogen spectrum was an early success of quantum mechanics^[39] and explained the Lamb shift observed in the hydrogen spectrum,^[40] which further led to the development of quantum electrodynamics.

Modern implementations of atomic spectroscopy for studying visible and ultraviolet transitions include flame emission spectroscopy, inductively coupled plasma atomic emission spectroscopy,^[41] glow discharge spectroscopy,^[42] microwave induced plasma spectroscopy,^[43] and spark or arc emission spectroscopy.^[44] Techniques for studying X-ray spectra include X-ray spectroscopy^[26] and X-ray fluorescence.^[45]

Molecules

The combination of atoms into molecules leads to the creation of unique types of energetic states and therefore unique spectra of the transitions between these states. Molecular spectra can be obtained due to electron spin states (electron paramagnetic resonance), molecular rotations, molecular vibration, and electronic states. Rotations are collective motions of the atomic nuclei and typically lead to spectra in the microwave and millimetre-wave spectral regions. Rotational spectroscopy and microwave spectroscopy are synonymous. Vibrations are relative motions of the atomic nuclei and are studied by both infrared and Raman spectroscopy. Electronic excitations are studied using visible and ultraviolet spectroscopy as well as fluorescence spectroscopy.^[32]^[46]^[47]^[48]^[49]

Studies in molecular spectroscopy led to the development of the first maser and contributed to the subsequent development of the laser.

Crystals and extended materials

The combination of atoms or molecules into crystals or other extended forms leads to the creation of additional energetic states. These states are numerous and therefore have a high density of states. This high density often makes the spectra weaker and less distinct, i.e., broader.Script error: No such module "Unsubst". For instance, blackbody radiation is due to the thermal motions of atoms and molecules within a material. Acoustic and mechanical responses are due to collective motions as well.Script error: No such module "Unsubst". Pure crystals, though, can have distinct spectral transitions, and the crystal arrangement has an effect on the observed molecular spectra. The regular lattice structure of crystals scatters X-rays,^[50] electrons,^[51] or neutrons,^[52] allowing for crystallographic studies.

Nuclei

Nuclei have distinct energy states that are widely separated and lead to gamma ray spectra.Script error: No such module "Unsubst". Distinct nuclear spin states can have their energy separated by a magnetic field, and this allows for nuclear magnetic resonance spectroscopy.^[53]

Other types

Script error: No such module "Unsubst". Other types of spectroscopy are distinguished by specific applications or implementations:

Acoustic resonance spectroscopy is based on sound waves primarily in the audible and ultrasonic regions.^[54]
Auger electron spectroscopy is a method used to study surfaces of materials on a micro-scale. It is often used in connection with electron microscopy.^[55]
Cavity ring-down spectroscopy enables measurement of absolute optical extinction by samples that scatter and absorb light.^[56]
Circular dichroism spectroscopy measures the differential absorption of left- and right-handed circularly polarized light.^[57]
Coherent anti-Stokes Raman spectroscopy is a recent technique that has high sensitivity and powerful applications for in vivo spectroscopy and imaging.^[58]
Cold vapour atomic fluorescence spectroscopy is a subclass of the atomic emission spectroscopy technique that measures trace amounts of volatile heavy metals in the air, such as mercury.^[59]
Correlation spectroscopy encompasses several types of two-dimensional NMR spectroscopy.^[60]
Deep-level transient spectroscopy measures concentration and analyzes parameters of electrically active defects in semiconducting materials.^[61]
Dielectric spectroscopy measures the dielectric properties of a medium as a function of frequency.^[62]
Dual-polarization interferometry measures the real and imaginary components of the complex refractive index.^[63]
Electron energy loss spectroscopy in transmission electron microscopy.^[64]
Electron phenomenological spectroscopy measures the physicochemical properties and characteristics of the electronic structure of multicomponent and complex molecular systems.^[65]
Electron paramagnetic resonance spectroscopy is similar to nuclear magnetic resonance (NMR), except it measures the spin excitement of unpaired electrons.^[66]
Force spectroscopy is a set of techniques for the study of the interactions and the binding forces between individual molecules, although the name is somewhat misleading because there is no true matter-radiation interaction.^[67]
Fourier-transform spectroscopy is an efficient method for processing spectra data obtained using interferometers. Fourier-transform infrared spectroscopy is an implementation of infrared spectroscopy.^[68] NMR also employs Fourier transforms.
Gamma spectroscopy measures the gamma ray emissions from high energy processes including radioactive and astrophysical sources.^[69]
Hadron spectroscopy studies the energy/mass spectrum of hadrons according to spin, parity, and other particle properties. Baryon spectroscopy and meson spectroscopy are types of hadron spectroscopy.
Multispectral imaging and hyperspectral imaging is a method to create a complete picture of the environment or various objects, each pixel containing a full visible, visible near infrared, near infrared, or infrared spectrum.^[70]
Inelastic electron tunneling spectroscopy uses the changes in current due to inelastic electron-vibration interaction at specific energies that can also measure optically forbidden transitions.^[71]
Inelastic neutron scattering is similar to Raman spectroscopy, but uses neutrons instead of photons.
Laser-induced breakdown spectroscopy, also called laser-induced plasma spectrometry
Laser spectroscopy uses tunable lasers^[72] and other types of coherent emission sources, such as optical parametric oscillators,^[73] for selective excitation of atomic or molecular species.
Light scattering spectroscopy (LSS) is a spectroscopic technique typically used to evaluate morphological changes in epithelial cells in order to study mucosal tissue and detect early cancer and precancer.^[11]^[74]
Mass spectroscopy is a historical term used to refer to mass spectrometry. The current recommendation is to use the latter term.^[75] The term "mass spectroscopy" originated in the use of phosphor screens to detect ions.
Mössbauer spectroscopy probes the properties of specific isotopic nuclei in different atomic environments by analyzing the resonant absorption of gamma rays. See Mössbauer effect.
Multivariate optical computing is an all optical compressed sensing technique, generally used in harsh environments, that directly calculates chemical information from a spectrum as analogue output.
Neutron spin echo spectroscopy measures internal dynamics in proteins and other soft matter systems.
Nuclear quadrupole resonance is a chemical spectroscopy method mediated by NMR of the electric field gradient (EFG) in the absence of magnetic field
Perturbed angular correlation (PAC) uses radioactive nuclei as probe to study electric and magnetic fields (hyperfine interactions) in crystals (condensed matter) and bio-molecules.
Photoacoustic spectroscopy is the measurement of the effect of absorbed electromagnetic energy on matter by means of acoustic detection.^[76]
Acoustic emission spectroscopy is the measurement of acoustic waves as a material is deformed.^[77]
Photoemission spectroscopy measures the energy or spin of electrons emitted from materials by the photoelectric effect.^[78]
Photothermal spectroscopy measures heat evolved upon absorption of radiation.
Pump-probe spectroscopy can use ultrafast laser pulses to measure reaction intermediates in the femtosecond timescale.
Raman optical activity spectroscopy exploits Raman scattering and optical activity effects to reveal detailed information on chiral centers in molecules.
Raman spectroscopy is used to determine vibrational modes of molecules, providing a structural fingerprint by which molecules can be identified.^[79]
Saturated spectroscopy
Scanning tunneling spectroscopy
Spectrophotometry
Spin noise spectroscopy traces spontaneous fluctuations of electronic and nuclear spins.^[80]
Time-resolved spectroscopy measures the decay rates of excited states using various spectroscopic methods.
Time-stretch spectroscopy^[81]^[82]
Thermal infrared spectroscopy measures thermal radiation emitted from materials and surfaces and is used to determine the type of bonds present in a sample as well as their lattice environment. The techniques are widely used by organic chemists, mineralogists, and planetary scientists.
Transient grating spectroscopy measures quasiparticle propagation. It can track changes in metallic materials as they are irradiated.
Ultraviolet photoelectron spectroscopy
Ultraviolet–visible spectroscopy
Vibrational circular dichroism spectroscopy
Video spectroscopy
X-ray photoelectron spectroscopy

Applications

File:UVES on UT2-KUEYEN.jpg

UVES is a high-resolution spectrograph on the Very Large Telescope.^[83]

There are several applications of spectroscopy in the fields of medicine, physics, chemistry, and astronomy. Taking advantage of the properties of absorbance and, with astronomy, emission, spectroscopy can be used to identify certain states of nature. The uses of spectroscopy in so many different fields and for so many different applications has caused specialty scientific subfields. Such examples include:

Determining the atomic structure of a sample^[84]
Studying spectral emission lines of the sun and distant galaxies^[85]
Space exploration^[86]
Cure monitoring of composites using optical fibers.^[87]
Estimating weathered wood exposure times using near infrared spectroscopy^[88]
Measurement of different compounds in food samples by absorption spectroscopy both in visible and infrared spectrum^[89]
Measurement of toxic compounds in blood samples
Non-destructive elemental analysis by X-ray fluorescence
Electronic structure research with various spectroscopes
Redshift to determine the speed and velocity of a distant object
Determining the metabolic structure of a muscle
Monitoring dissolved oxygen content in freshwater and marine ecosystems
Altering the structure of drugs to improve effectiveness
Characterization of proteins
Respiratory gas analysis in hospitals^[8]
Finding the physical properties of a distant star or nearby exoplanet using the Relativistic Doppler effect.^[90]
In-ovo sexing: spectroscopy allows to determine the sex of the egg while it is hatching. Developed by French and German companies, both countries decided to ban chick culling, mostly done through a macerator, in 2022.^[91]
Process monitoring in Industrial process control^[92]

History

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The history of spectroscopy began with Isaac Newton's optics experiments (1666–1672). According to Andrew Fraknoi and David Morrison, "In 1672, in the first paper that he submitted to the Royal Society, Isaac Newton described an experiment in which he permitted sunlight to pass through a small hole and then through a prism. Newton found that sunlight, which looks white to us, is actually made up of a mixture of all the colors of the rainbow."^[93] Newton applied the word "spectrum" to describe the rainbow of colors that combine to form white light and that are revealed when the white light is passed through a prism.

Fraknoi and Morrison state that "In 1802, William Hyde Wollaston built an improved spectrometer that included a lens to focus the Sun's spectrum on a screen. Upon use, Wollaston realized that the colors were not spread uniformly, but instead had missing patches of colors, which appeared as dark bands in the spectrum."^[93] During the early 1800s, Joseph von Fraunhofer made experimental advances with dispersive spectrometers that enabled spectroscopy to become a more precise and quantitative scientific technique. Since then, spectroscopy has played and continues to play a significant role in chemistry, physics, and astronomy. Per Fraknoi and Morrison, "Later, in 1815, German physicist Joseph Fraunhofer examined the solar spectrum, and found about 600 such dark lines (missing colors), are now known as Fraunhofer lines, or Absorption lines."^[93]Template:Better source needed

Spectra of atoms and molecules often consist of a series of spectral lines, each one representing a resonance between two different quantum states. The explanation of these series, and the spectral patterns associated with them, were one of the experimental enigmas that drove the development and acceptance of quantum mechanics. The hydrogen spectral series in particular was first successfully explained by the Rutherford–Bohr quantum model of the hydrogen atom. In some cases spectral lines are well separated and distinguishable, but spectral lines can overlap and appear to be a single transition if the density of energy states is high enough. Named series of lines include the principal, sharp, diffuse and fundamental series.

Hobbyist

Spectroscopy has emerged as a growing practice within the maker movement, enabling hobbyists and educators to construct functional spectrometers using readily available materials.^[94] Utilizing components like CD/DVD diffraction gratings, smartphones, and 3D-printed parts, these instruments offer a hands-on approach to understanding light and matter interactions. Smartphone applications^[95]^[96] along with open-source tools^[97] facilitate integration, greatly simplify the capturing and analysis of spectral data. While limitations in resolution, calibration accuracy, and stray light management exist compared to professional equipment, DIY spectroscopy provides valuable educational experiences^[98] and contributes to citizen science initiatives, fostering accessibility to spectroscopic techniques.

References

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External links

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Spectroscopy: Difference between revisions

Latest revision as of 13:55, 31 December 2025

Contents

Introduction

Theory

Classification of methods

Type of radiative energy

Nature of the interaction

Type of material

Atoms

Molecules

Crystals and extended materials

Nuclei

Other types

Applications

History

Hobbyist

See also

References

Further reading

External links

Navigation menu

@@ Line 1: / Line 1: @@
 {{Short description|Study involving matter and electromagnetic radiation}}
-{{More citations needed|date=April 2016}}
+[[File:Light dispersion of a mercury-vapor lamp with a flint glass prism IPNr°0125.jpg|thumb|A [[Prism (optics)|prism]] separates white light by [[Dispersion (optics)|dispersing]] it into its component colors, which can then be studied using spectroscopy.]]
-[[File:Light dispersion of a mercury-vapor lamp with a flint glass prism IPNr°0125.jpg|thumb|An example of spectroscopy: a [[Prism (optics)|prism]] separates white light by [[Dispersion (optics)|dispersing]] it into its component colors.]]
-'''Spectroscopy''' is the field of study that measures and interprets [[electromagnetic spectrum|electromagnetic spectra]].<ref>{{Cite book |last1=Duckett |first1=Simon |title=Foundations of Spectroscopy |last2=Gilbert |first2=Bruce |publisher=Oxford Science Publications |year=2000 |isbn=978-0198503354}}</ref><ref name="Crouch-Skoog-Holler2007" /> In narrower contexts, spectroscopy is the precise study of [[color]] as generalized from [[visible light]] to all bands of the electromagnetic spectrum.
+'''Spectroscopy''' is the field of study that measures and interprets [[electromagnetic spectrum|electromagnetic spectra]] as it interacts with matter.<ref>{{cite book | chapter=Introduction | title=Atomic Emission Spectrometry: AES - Spark, Arc, Laser Excitation | first1=Heinz-Gerd | last1=Joosten | first2=Alfred | last2=Golloch | first3=Jörg | last3=Flock | first4=Susan | last4=Killewald | publisher=Walter de Gruyter GmbH & Co KG | year=2020 | page=1 | doi=10.1515/9783110529692-001 | isbn=978-3-11-052969-2 | chapter-url=https://books.google.com/books?id=dhTzDwAAQBAJ&pg=PA1 }}</ref> In narrower contexts, spectroscopy is the precise study of [[color]] as generalized from radiated [[visible light]] to all bands of the electromagnetic spectrum.
-Spectroscopy, primarily in the electromagnetic spectrum, is a fundamental exploratory tool in the fields of [[astronomy]], [[chemistry]], [[materials science]], and [[physics]], allowing the composition, physical structure and electronic structure of matter to be investigated at the atomic, [[molecule|molecular]] and macro scale, and over [[Distance measures (cosmology)|astronomical distances]].
+Spectroscopy, primarily in the electromagnetic spectrum, is a fundamental exploratory tool in the fields of [[astronomy]], [[chemistry]], [[materials science]], and [[physics]], allowing the composition, physical and electronic structure of matter to be investigated at the atomic, [[molecule|molecular]] and macro scale, and over [[Distance measures (cosmology)|astronomical distances]].
-Historically, spectroscopy originated as the study of the wavelength dependence of the absorption by gas phase matter of visible light dispersed by a [[Prism (optics)|prism]]. Current applications of spectroscopy include [[biomedical spectroscopy]] in the areas of [[tissue (biology)|tissue]] analysis and [[medical imaging]]. [[Matter wave]]s and [[acoustic wave]]s can also be considered forms of radiative energy, and recently [[gravitational wave]]s have been associated with a spectral signature in the context of the [[LIGO|Laser Interferometer Gravitational-Wave Observatory]] (LIGO).<ref>{{Citation |last=Bartusiak |first=Marcia |title=Einstein's Unfinished Symphony: The Story of a Gamble, Two Black Holes, and a New Age of Astronomy |date=2017-06-27 |url=https://www.degruyter.com/document/doi/10.12987/9780300228120/html |work=Einstein’s Unfinished Symphony |access-date=2023-05-22 |publisher=Yale University Press |language=en |doi=10.12987/9780300228120 |oclc=1039140043 |isbn=9780300228120|s2cid=246149887 |url-access=subscription }} [https://books.google.com/books?id=6mMlDwAAQBAJ Google Books]</ref>
+Historically, spectroscopy originated as the study of the wavelength dependence of the absorption by gas phase matter of visible light dispersed by a [[Prism (optics)|prism]]. Current applications of spectroscopy include [[biomedical spectroscopy]] in the areas of [[tissue (biology)|tissue]] analysis and [[medical imaging]]. [[Matter wave]]s and [[acoustic wave]]s can be considered forms of radiative energy, and recently [[gravitational wave]]s have been associated with a spectral signature in the context of the [[LIGO|Laser Interferometer Gravitational-Wave Observatory]] (LIGO).<ref>{{Citation |last=Bartusiak |first=Marcia |title=Einstein's Unfinished Symphony: The Story of a Gamble, Two Black Holes, and a New Age of Astronomy |date=2017-06-27 |url=https://www.degruyter.com/document/doi/10.12987/9780300228120/html |work=Einstein's Unfinished Symphony |access-date=2023-05-22 |publisher=Yale University Press |language=en |doi=10.12987/9780300228120 |oclc=1039140043 |isbn=978-0-300-22812-0|s2cid=246149887 |url-access=subscription }} [https://books.google.com/books?id=6mMlDwAAQBAJ Google Books]</ref>
 == Introduction ==
-Spectroscopy is a branch of science concerned with the [[spectrum|spectra]] of [[electromagnetic radiation]] as a function of its wavelength or frequency measured by [[spectrograph]]ic equipment, and other techniques, in order to obtain information concerning the structure and properties of matter.<ref>{{Cite book |url=https://books.google.com/books?id=U5MdAQAAIAAJ |title=The Oxford American College Dictionary |date=2002 |publisher=G.P. Putnam's Sons |isbn=9780399144158 |oclc=48965005}}</ref> Spectral measurement devices are referred to as [[spectrometers]], [[spectrophotometers]], [[spectrograph]]s or [[spectral analyzer]]s. Most spectroscopic analysis in the laboratory starts with a sample to be analyzed, then a light source is chosen from any desired range of the light spectrum, then the light goes through the sample to a dispersion array (diffraction grating instrument) and captured by a [[photodiode]]. For astronomical purposes, the telescope must be equipped with the light dispersion device. There are various versions of this basic setup that may be employed.
+Spectroscopy is a branch of science concerned with the [[spectrum|spectra]] of [[electromagnetic radiation]] as a function of its [[wavelength]] or [[frequency]], as measured by [[spectrograph]]ic equipment and other techniques, in order to obtain information concerning the structure and properties of matter.<ref>{{Cite book | url=https://books.google.com/books?id=U5MdAQAAIAAJ | title=The Oxford American College Dictionary | date=2002 | publisher=G.P. Putnam's Sons | isbn=978-0-399-14415-8 | oclc=48965005}}</ref> Spectral measurement devices are referred to as [[spectrometers]], [[spectrophotometers]], [[spectrograph]]s or [[spectral analyzer]]s. Most spectroscopic analysis in the laboratory starts with a sample to be analyzed. A light source is sent through a [[monochromator]] to spatially separate the colors before passing a selected frequency band through the sample, then the output is captured by a [[photodiode]].<ref name=Hammes_2005>{{cite book | title=Spectroscopy for the Biological Sciences | first=Gordon G. | last=Hammes | publisher=John Wiley & Sons | year=2005 | isbn=978-0-471-73354-6 | pages=36–37 | url=https://books.google.com/books?id=glECXyfF4dcC&pg=PA37 }}</ref> For astronomical purposes, the telescope must be equipped with the [[Dispersion (optics)|light dispersion]] device.<ref>{{cite book | title=Fundamental Astronomy | editor1-first=Hannu | editor1-last=Karttunen | editor2-first=Pekka | editor2-last=Kröger | editor3-first=Heikki | editor3-last=Oja | editor4-first=Markku | editor4-last=Poutanen | editor5-first=Karl Johan | editor5-last=Donner | edition=6th | publisher=Springer | year=2016 | isbn=978-3-662-53045-0 | page=73 | url=https://books.google.com/books?id=ndd2DQAAQBAJ&pg=PA73 }}</ref> There are various versions of this basic setup that may be employed.
-Spectroscopy began with [[Isaac Newton]] splitting light with a prism; a key moment in the development of modern [[optics]].<ref>"[https://www.aaas.org/isaac-newton-and-problem-color Isaac Newton and the problem of color]", Steven A. Edwards, AAAS.</ref> Therefore, it was originally the study of visible light that we call [[color]] that later under the studies of [[James Clerk Maxwell]] came to include the entire [[electromagnetic spectrum]].<ref>{{cite web|url=http://www.kcl.ac.uk/newsevents/news/newsrecords/2011/04Apr/JamesClerkMaxwell.aspx |title=1861: James Clerk Maxwell's greatest year |date=18 April 2011 |publisher=King's College London |access-date=28 March 2013 |url-status=dead |archive-url=https://web.archive.org/web/20130622095747/http://www.kcl.ac.uk/newsevents/news/newsrecords/2011/04Apr/JamesClerkMaxwell.aspx |archive-date=22 June 2013 }}</ref> Although color is involved in spectroscopy, it is not equated with the color of elements or objects that involve the absorption and reflection of certain electromagnetic waves to give objects a sense of color to our eyes. Rather spectroscopy involves the splitting of light by a prism, diffraction grating, or similar instrument, to give off a particular discrete line pattern called a "spectrum" unique to each different type of element. Most elements are first put into a gaseous phase to allow the spectra to be examined although today other methods can be used on different phases. Each element that is diffracted by a prism-like instrument displays either an absorption spectrum or an emission spectrum depending upon whether the element is being cooled or heated.<ref name="auto">PASCO, "[https://www.pasco.com/products/guides/what-is-spectroscopy What is Spectroscopy?]"</ref>
+[[File:High resolution solar spectrum (noao-sun).jpg|right|thumb|High resolution spectrum of the Sun, showing the discrete line pattern created by elements in the [[stellar atmosphere]]]]
+Spectroscopy began with [[Isaac Newton]] splitting light with a prism; a key moment in the development of modern [[optics]].<ref>{{cite web | url=https://www.aaas.org/isaac-newton-and-problem-color | date=19 November 2012 | access-date=2025-11-23 | title=Isaac Newton and the problem of color | first=Steven A. | last=Edwards | publisher=American Association for the Advancement of Science }}</ref> Therefore, it was originally the study of [[visible light]] that we call [[color]]. Following the contributions of [[James Clerk Maxwell]], this study later came to include the entire [[electromagnetic spectrum]].<ref>{{cite web | title=1861: James Clerk Maxwell's greatest year | date=18 April 2011 | publisher=King's College London | url=http://www.kcl.ac.uk/newsevents/news/newsrecords/2011/04Apr/JamesClerkMaxwell.aspx | access-date=28 March 2013 | archive-url=https://web.archive.org/web/20130622095747/http://www.kcl.ac.uk/newsevents/news/newsrecords/2011/04Apr/JamesClerkMaxwell.aspx | archive-date=22 June 2013 }}</ref> Although color is involved in spectroscopy, it is not equivalent to the [[Absorption (electromagnetic radiation)|absorption]] and [[Reflection (physics)|reflection]] of certain electromagnetic waves that give objects or elements a sense of color to our eyes. Rather, spectroscopy involves the splitting of light by a prism, diffraction grating, or similar instrument, to display a particular discrete line pattern called a "spectrum", which is unique for each different type of element or molecule. Most elements are first put into a gaseous state to allow the spectra to be examined, although today other methods can be used for different [[Phase (matter)|phases]] of matter. Each element that is diffracted by a prism-like instrument displays either an absorption spectrum or an emission spectrum depending upon whether the element is being cooled or heated.<ref name="auto">{{cite web | publisher=PASCO | url=https://www.pasco.com/products/guides/what-is-spectroscopy | title=What is Spectroscopy? | archive-url=https://web.archive.org/web/20230614114048/https://www.pasco.com/products/guides/what-is-spectroscopy | archive-date=2023-06-14 | url-status=dead }}</ref>
-Until recently all spectroscopy involved the study of line spectra and most spectroscopy still does.<ref>Sutton, M. A. "[http://www.jstor.org/stable/4025175 Sir John Herschel and the Development of Spectroscopy in Britain]". The British Journal for the History of Science, vol. 7, no. 1, [Cambridge University Press, The British Society for the History of Science], 1974, pp. 42–60.</ref> Vibrational spectroscopy is the branch of spectroscopy that studies the spectra.<ref>Lazić, Dejan. "Introduction to Raman Microscopy/Spectroscopy". Application of Molecular Methods and Raman Microscopy/Spectroscopy in Agricultural Sciences and Food Technology, edited by Dejan Lazić et al., Ubiquity Press, 2019, pp. 143–50, http://www.jstor.org/stable/j.ctvmd85qp.12.
+Until recently all spectroscopy involved the study of line spectra and most spectroscopy still does.<ref>{{cite journal | last=Sutton | first=M. A. | title=Sir John Herschel and the Development of Spectroscopy in Britain | journal=The British Journal for the History of Science | volume=7 | issue=1 | publisher=Cambridge University Press | year=1974 | pages=42–60 | jstor=4025175 | doi=10.1017/S0007087400012851  }}</ref> Vibrational spectroscopy is the branch of spectroscopy that studies the spectra.<ref>{{cite book | last=Lazić | first=Dejan | chapter=Introduction to Raman Microscopy/Spectroscopy | title=Application of Molecular Methods and Raman Microscopy/Spectroscopy in Agricultural Sciences and Food Technology | editor1-first=Biljana Vucelić | editor-last=Radović | editor2-first=Dejan | editor2-last=Lazić | editor3-first=Miomir | editor3-last=Nikšić | location=London | publisher=Ubiquity Press | year=2019 | pages=143–50 | jstor=j.ctvmd85qp.12 | doi=10.5334/bbj.i| isbn=978-1-911529-52-1 | doi-access=free }}</ref> However, the latest developments in spectroscopy can sometimes dispense with the dispersion technique. In biochemical spectroscopy, information can be gathered about biological tissue by absorption and light scattering techniques. Light scattering spectroscopy is a type of reflectance spectroscopy that determines tissue structures by examining elastic scattering.<ref name="link.aps.org">{{Cite journal |last1=Perelman |first1=L. T. |last2=Backman |first2=V. |last3=Wallace |first3=M. |last4=Zonios |first4=G. |last5=Manoharan |first5=R. |last6=Nusrat |first6=A. |last7=Shields |first7=S. |last8=Seiler |first8=M. |last9=Lima |first9=C. |last10=Hamano |first10=T. |last11=Itzkan |first11=I. |last12=Van Dam |first12=J. |last13=Crawford |first13=J. M. |last14=Feld |first14=M. S. |date=1998-01-19 |title=Observation of Periodic Fine Structure in Reflectance from Biological Tissue: A New Technique for Measuring Nuclear Size Distribution |url=https://link.aps.org/doi/10.1103/PhysRevLett.80.627 |journal=Physical Review Letters |volume=80 |issue=3 |pages=627–630 |doi=10.1103/PhysRevLett.80.627|bibcode=1998PhRvL..80..627P |url-access=subscription }}</ref> In such a case, it is the tissue that acts as a diffraction or dispersion mechanism.
-</ref> However, the latest developments in spectroscopy can sometimes dispense with the dispersion technique. In biochemical spectroscopy, information can be gathered about biological tissue by absorption and light scattering techniques. Light scattering spectroscopy is a type of reflectance spectroscopy that determines tissue structures by examining elastic scattering.<ref name="link.aps.org">{{Cite journal |last1=Perelman |first1=L. T. |last2=Backman |first2=V. |last3=Wallace |first3=M. |last4=Zonios |first4=G. |last5=Manoharan |first5=R. |last6=Nusrat |first6=A. |last7=Shields |first7=S. |last8=Seiler |first8=M. |last9=Lima |first9=C. |last10=Hamano |first10=T. |last11=Itzkan |first11=I. |last12=Van Dam |first12=J. |last13=Crawford |first13=J. M. |last14=Feld |first14=M. S. |date=1998-01-19 |title=Observation of Periodic Fine Structure in Reflectance from Biological Tissue: A New Technique for Measuring Nuclear Size Distribution |url=https://link.aps.org/doi/10.1103/PhysRevLett.80.627 |journal=Physical Review Letters |volume=80 |issue=3 |pages=627–630 |doi=10.1103/PhysRevLett.80.627|bibcode=1998PhRvL..80..627P |url-access=subscription }}</ref> In such a case, it is the tissue that acts as a diffraction or dispersion mechanism.
-Spectroscopic studies were central to the development of [[quantum mechanics]], because the first useful atomic models described the spectra of hydrogen, which include the [[Bohr model]], the [[Schrödinger equation]], and [[Matrix mechanics]], all of which can produce the spectral lines of [[hydrogen]], therefore providing the basis for discrete quantum jumps to match the discrete hydrogen spectrum. Also, [[Max Planck]]'s explanation of [[blackbody radiation]] involved spectroscopy because he was comparing the wavelength of light using a photometer to the temperature of a [[Black Body]].<ref>Kumar, Manjit. Quantum: Einstein, Bohr, and the great debate about the nature of reality / Manjit Kumar.—1st American ed., 2008. Chap.1.</ref> Spectroscopy is used in [[physical chemistry|physical]] and [[analytical chemistry]] because [[atoms]] and [[molecules]] have unique spectra. As a result, these spectra can be used to detect, identify and quantify information about the atoms and molecules. Spectroscopy is also used in [[astronomical spectroscopy|astronomy]] and [[remote sensing]] on Earth. Most research [[telescopes]] have spectrographs. The measured spectra are used to determine the chemical composition and [[physical property|physical properties]] of [[astronomical objects]] (such as their [[temperature]], density of elements in a star, [[velocity]], [[black holes]] and more).<ref>{{cite web |title=Spectra and What They Can Tell Us |publisher=NASA Goddard Space Flight Center |url=https://imagine.gsfc.nasa.gov/science/toolbox/spectra1.html |date=August 2013 |website=Imagine the Universe! }}</ref> An important use for spectroscopy is in biochemistry. Molecular samples may be analyzed for species identification and energy content.<ref>{{cite web |title=Basic Spectroscopy |first1=Santi |last1=Nonell|first2=Cristiano |last2=Viappiani |url=http://photobiology.info/Nonell_Viappiani.html |website=Photobiological Sciences Online }}</ref>
+Spectroscopic studies were central to the development of [[quantum mechanics]]. The first useful quantum atomic models, including [[Bohr model]], the [[Schrödinger equation]], and [[Matrix mechanics]], reproduced the spectral lines of [[hydrogen]]. These equated discrete quantum jumps of the bound electron in a hydrogen atom to the discrete hydrogen spectrum. [[Max Planck]]'s explanation of [[blackbody radiation]] involved spectroscopy because he was comparing the wavelength of light using a photometer to the temperature of a [[Black Body]].<ref>{{cite book | last=Kumar | first=Manjit | chapter=Chap. 1 | title=Quantum: Einstein, Bohr, and the great debate about the nature of reality | edition=1st American | year=2008 | publisher=W. W. Norton & Co. | isbn=978-1-84831-103-9 | url=https://dokumen.pub/quantum-einstein-bohr-and-the-great-debate-about-the-nature-of-reality-9781848311039-1848311036.html | access-date=2025-11-23 }}</ref> Spectroscopy is used in [[physical chemistry|physical]] and [[analytical chemistry]] because [[atoms]] and [[molecules]] have unique spectra. As a result, these spectra can be used to detect, identify and quantify information about the atoms and molecules.
+Spectroscopy is used in [[astronomical spectroscopy|astronomy]] and [[remote sensing]] on Earth. Most research [[telescopes]] have spectrographs. The measured spectra are used to determine the chemical composition and [[physical property|physical properties]] of [[astronomical objects]], such as their [[temperature]], elemental abundances, [[velocity]], rotation, [[stellar magnetic field|magnetic field]], and more.<ref>{{cite web | title=Spectra and What They Can Tell Us | publisher=NASA Goddard Space Flight Center | url=https://imagine.gsfc.nasa.gov/science/toolbox/spectra1.html | date=August 2013 | website=Imagine the Universe! | access-date=2025-11-23 }}</ref> An important use for spectroscopy is in biochemistry. Molecular samples may be analyzed for species identification and energy content.<ref>{{cite web | title=Basic Spectroscopy | date=16 October 2008 | first1=Santi | last1=Nonell | first2=Cristiano | last2=Viappiani | url=http://photobiology.info/Nonell_Viappiani.html | website=Photobiological Sciences Online | access-date=2025-11-23 }}</ref>
 == Theory ==
-The underlying premise of spectroscopy is that light is made of different wavelengths and that each wavelength corresponds to a different frequency. The importance of spectroscopy is centered around the fact that every element in the [[periodic table]] has a unique light spectrum described by the frequencies of light it emits or absorbs consistently appearing in the same part of the electromagnetic spectrum when that light is diffracted. This opened up an entire field of study with anything that contains atoms. Spectroscopy is the key to understanding the atomic properties of all matter. As such spectroscopy opened up many new sub-fields of science yet undiscovered. The idea that each atomic element has its unique spectral signature enabled spectroscopy to be used in a broad number of fields each with a specific goal achieved by different spectroscopic procedures. The [[National Institute of Standards and Technology]] maintains a public Atomic Spectra Database that is continually updated with precise measurements.<ref>"[https://www.nist.gov/pml/atomic-spectra-database Atomic Spectra Database]", NIST.</ref>
+The underlying premise of spectroscopy is that light is made of different wavelengths and that each wavelength corresponds to a different frequency. The importance of spectroscopy is centered around the fact that every element in the [[periodic table]] has a unique light spectrum described by the frequencies of light it emits or absorbs consistently appearing in the same part of the electromagnetic spectrum when that light is diffracted.<ref>{{cite web | title=Spectroscopy 101 – Types of Spectra and Spectroscopy | publisher=NASA | date=September 9, 2025 | editor-first=Stephen | editor-last=Sabia | url=https://science.nasa.gov/mission/webb/science-overview/science-explainers/spectroscopy-101-types-of-spectra-and-spectroscopy/ | access-date=2025-12-02 }}</ref> This opened up an entire field of study with anything that contains atoms. Spectroscopy is the key to understanding the atomic properties of all matter. As such spectroscopy opened up many new sub-fields of science yet undiscovered. The idea that each atomic element has its unique spectral signature enabled spectroscopy to be used in a broad number of fields each with a specific goal achieved by different spectroscopic procedures. The [[National Institute of Standards and Technology]] maintains a public Atomic Spectra Database that is continually updated with precise measurements.<ref>{{cite journal | last1=Kramida | first1=Alexander | last2=Ralchenko | first2=Yuri | title=Atomic Spectra Database | journal=NIST Standard Reference Database 78 | version=5.12 | date=November 2024 | publisher=[[National Institute of Standards and Technology]] | doi=10.18434/T4W30F | url=https://www.nist.gov/pml/atomic-spectra-database | access-date=2025-11-24 }}</ref>
+With an absorption spectrophotometer, the level of absorption of a light source is determined by the [[Beer-Lambert Law]]:
+<math display="block">\ln\left(\frac{I_0}{I}\right)=\varepsilon \ell c</math>
+where <math>I_0</math> is the light intensity before passing through the sample, <math>I</math> is the output intensity, <math>\varepsilon</math> is the extinction coefficient, <math>\ell</math> is the path length through the sample, and <math>c</math> is the concentration of the sample. The extinction coefficient depends on the wavelength selected and the molecule being sampled.<ref name=Hammes_2005/>
+Resonances by the frequency were first characterized in mechanical systems such as [[pendulums]], which have a frequency of motion noted famously by [[Galileo]].<ref>{{cite book | first=Isaac | last=Asimov | author-link=Isaac Asimov | title=Understanding Physics | series=Dorset Press Reprints Series | volume=1 | page=108 | orig-date=1966 | year=1988 | publisher=Barnes & Noble Publishing | isbn=978-0-88029-251-1 | url=https://books.google.com/books?id=pSKvaLV6zkcC&pg=PA108 }}</ref> In quantum mechanical systems, the analogous resonance is a coupling of two quantum mechanical [[stationary state]]s of a system, such as two [[atomic orbital]]s, via an oscillatory source of energy such as a [[photon]]. The coupling of the two states is strongest when the source energy matches the energy difference between the two states.{{cn|date=November 2025|reason=Sources don't describe a quantum jump as a resonance between states.}} That is, a photon at the right energy is more likely to cause an electron to jump between two orbitals, a process called [[electron excitation]]. The energy {{mvar|E}} of a photon is related to its frequency {{mvar|ν}} by {{math|''E'' {{=}} ''hν''}} where {{mvar|h}} is the [[Planck constant]],<ref>{{cite web | title=Energy, Frequency, and Wavelength | work=3.091: Introduction to Solid State Chemistry | first=Maddie | last=Sutula | date=Fall 2018 | publisher=Massachusetts Institute of Technology | url=https://ocw.mit.edu/courses/3-091-introduction-to-solid-state-chemistry-fall-2018/50e1280c59c49bcc1dda8fc57834e150_MIT3_091F18_REC4.pdf | access-date=2025-11-27 }}</ref> and so a spectrum of the system response vs. photon frequency will peak at the resonant frequency or energy.
-The broadening of the field of spectroscopy is due to the fact that any part of the electromagnetic spectrum may be used to analyze a sample from the infrared to the ultraviolet telling scientists different properties about the very same sample. For instance in chemical analysis, the most common types of spectroscopy include atomic spectroscopy, infrared spectroscopy, ultraviolet and visible spectroscopy, [[Raman spectroscopy]] and [[nuclear magnetic resonance]].<ref>Saul, Louise. (April 6, 2020). "[https://www.azooptics.com/Article.aspx?ArticleID=1382 The Different Types of Spectroscopy for Chemical Analysis]". AZoOptics. Retrieved on November 10, 2021.</ref> In nuclear magnetic resonance (NMR), the theory behind it is that frequency is analogous to [[resonance]] and its corresponding resonant frequency. Resonances by the frequency were first characterized in mechanical systems such as [[pendulums]], which have a frequency of motion noted famously by [[Galileo]].<ref>Isaac Asimov, Understanding Physics, Vol. 1, p.108.</ref>
+Any part of the electromagnetic spectrum may be used to analyze a sample from the infrared to the ultraviolet telling scientists different properties about the very same sample, a discovery that led to a broadening of the field of spectroscopy. For instance in chemical analysis, the most common types of spectroscopy include atomic spectroscopy, infrared spectroscopy, ultraviolet and visible spectroscopy, [[Raman spectroscopy]] and [[nuclear magnetic resonance]].<ref>{{cite web | last=Saul | first=Louise | date=January 9, 2019 | url=https://www.azooptics.com/Article.aspx?ArticleID=1382 | title=The Different Types of Spectroscopy for Chemical Analysis | publisher=AZO Optics | access-date=2021-11-10 }}</ref> In nuclear magnetic resonance (NMR), the theory behind it is that frequency is analogous to [[resonance]] and its corresponding resonant frequency.
 == Classification of methods ==
-[[File:A Taste of ESPRESSO.jpg|thumb|A huge diffraction grating at the heart of the ultra-precise [[ESPRESSO]] spectrograph.<ref>{{cite web|title=A Taste of ESPRESSO|url=http://www.eso.org/public/images/potw1537a/|access-date=15 September 2015}}</ref>]]
+[[File:A Taste of ESPRESSO.jpg|thumb|A huge diffraction grating at the heart of the ultra-precise [[ESPRESSO]] spectrograph.<ref>{{cite web | title=A Taste of ESPRESSO | publisher=The European Southern Observatory | date=14 September 2015 | url=http://www.eso.org/public/images/potw1537a/ | access-date=15 September 2015 }}</ref>]]
 Spectroscopy is a sufficiently broad field that many sub-disciplines exist, each with numerous implementations of specific spectroscopic techniques. The various implementations and techniques can be classified in several ways.
 === Type of radiative energy ===
 The types of spectroscopy are distinguished by the type of radiative energy involved in the interaction. In many applications, the spectrum is determined by measuring changes in the intensity or frequency of this energy. The types of radiative energy studied include:
-* [[Electromagnetic radiation]] was the first source of energy used for spectroscopic studies. Techniques that employ electromagnetic radiation are typically classified by the wavelength region of the spectrum and include [[microwave spectroscopy|microwave]], [[terahertz spectroscopy and technology|terahertz]], [[infrared spectroscopy|infrared]], [[near-infrared spectroscopy|near-infrared]], [[Ultraviolet–visible spectroscopy|ultraviolet-visible]], [[x-ray spectroscopy|x-ray]], and [[gamma spectroscopy|gamma]] spectroscopy.
+* [[Electromagnetic radiation]] was the first source of energy used for spectroscopic studies. Techniques that employ electromagnetic radiation are typically classified by the wavelength region of the spectrum and include [[microwave spectroscopy|microwave]],<ref>{{cite journal | title=Microwave Spectroscopy | first=C. H. | last=Townes | journal=American Scientist | volume=40 | issue=2 | date=April 1952 | pages=270–290 | publisher=Sigma Xi, The Scientific Research Honor Society | jstor=27826432 }}</ref> [[terahertz spectroscopy|terahertz]],<ref>{{cite journal | title=Terahertz spectroscopy and imaging – Modern techniques and applications | first1=P. U. | last1=Jepsen | first2=D. G. | last2=Cooke | first3=M. | last3=Koch | journal=Laser & Photonics Reviews | volume=5 | issue=1 | date=January 2011 | pages=124–166 | doi=10.1002/lpor.201000011 }}</ref> [[infrared spectroscopy|infrared]],<ref>{{cite journal | title=Infrared Spectroscopy | first1=Lily M. | last1=Ng | first2=Reiko | last2=Simmons | journal=Analytical Chemistry | volume=71 | issue=12 | date=May 20, 1999 | publisher=American Chemical Society | doi=10.1021/a1999908r }}</ref> [[near-infrared spectroscopy|near-infrared]],<ref>{{cite journal | title=Principles, Techniques, and Limitations of Near Infrared Spectroscopy | first1=Marco | last1=Ferrari | first2=Leonardo | last2=Mottola | first3=Valentina | last3=Quaresima | journal=Canadian Journal of Applied Physiology | volume=29 | issue=4 | date=August 2004 | doi=10.1139/h04-031 }}</ref> [[Ultraviolet–visible spectroscopy|ultraviolet-visible]],<ref>{{cite journal | title=UV-Vis spectroscopy | last1=Picollo | first1=Marcello | last2=Aceto | first2=Maurizio | last3=Vitorino | first3=Tatiana | journal=Physical Sciences Reviews | volume=4 | issue=4 | year=2019 | article-number=20180008   | doi=10.1515/psr-2018-0008 }}</ref> [[x-ray spectroscopy|X-ray]],<ref name=Hippert_et_al_eds_2005/> and [[gamma spectroscopy|gamma]] spectroscopy.<ref>{{cite book | chapter=Gamma-Ray Spectroscopy | last1=Dunn | first1=W. L. | last2=McGregor | first2=D. S. | last3=Shultis | first3=J. K. | year=2021 | editor1-last=Fleck | editor1-first=I. | editor2-last=Titov | editor2-first=M. | editor3-last=Grupen | editor3-first=C. | editor4-last=Buvat | editor4-first=I. | title=Handbook of Particle Detection and Imaging | publisher=Springer, Cham. | doi=10.1007/978-3-319-93785-4_17 }}</ref>
-* Particles, because of their [[Matter wave|de Broglie waves]], can also be a source of radiative energy. Both [[electron spectroscopy|electron]] and [[neutron spectroscopy]] are commonly used. For a particle, its [[kinetic energy]] determines its wavelength.
+* Particles, because of their [[Matter wave|de Broglie waves]], can be a source of radiative energy.<ref name=Anderson_2025>{{cite book | title=Physics and Modern Life: A Panoramic Overview of the Fundamental Science and Its Human Impact | first=Michael | last=Anderson | publisher=Springer Nature | year=2025 | pages=473–474 | isbn=978-3-031-77825-4 | url=https://books.google.com/books?id=gaVjEQAAQBAJ&pg=PA473 }}</ref> Both [[electron spectroscopy|electron]]<ref>{{cite book | title=Electron Scattering and Related Spectroscopies | first1=Maurizio | last1=De Crescenzi | first2=M. Novella | last2=Piancastelli | publisher=World Scientific | year=1996 | isbn=9789810223007 | pages=1–5 | url=https://books.google.com/books?id=HzEN5tPPzuwC&pg=PA11 }}</ref> and [[neutron spectroscopy]] are  used.<ref name=Hippert_et_al_eds_2005>{{cite book | title=Neutron and X-ray Spectroscopy | editor1-first=Françoise | editor1-last=Hippert | editor2-first=Erik | editor2-last=Geissler | editor3-first=Jean Louis | editor3-last=Hodeau | editor4-first=Eddy | editor4-last=Lelièvre-Berna | editor5-first=Jean-René | editor5-last=Regnard | publisher=Springer Science & Business Media | year=2005 | ISBN=978-1-4020-3336-0 | url=https://books.google.com/books?id=C03N3xu8UWUC&pg=PR23 }}</ref> For a particle, its [[kinetic energy]] determines its wavelength.<ref name=Anderson_2025/>
-* [[Spectrogram|Acoustic spectroscopy]] involves radiated pressure waves.
+* [[Spectrogram|Acoustic spectroscopy]] involves radiated pressure waves.<ref>{{cite encyclopedia | title=Acoustic Spectrometer, Acoustic Spectrometry of Solids | encyclopedia=Encyclopedic Dictionary of Condensed Matter Physics | first=Charles P. | last=Poole Jr. | publisher=Academic Press | year=2004 | isbn=978-0-470-23300-9 | page=13–15 | url=https://books.google.com/books?id=CXwrqM2hU0EC&pg=PA14 }}</ref>
-* [[Dynamic mechanical analysis]] can be employed to impart radiating energy, similar to acoustic waves, to solid materials.
+* [[Dynamic mechanical analysis]] can be employed to impart radiating energy, similar to acoustic waves, to solid materials.<ref>{{cite book | chapter=Dynamic Mechanical Analysis | title=Characterization and Analysis of Polymers | publisher=John Wiley & Sons | year=2008 | isbn=978-0-470-23300-9 | page=649 | chapter-url=https://books.google.com/books?id=IWqmp9oMToIC&pg=PA649 }}</ref>
 === Nature of the interaction ===
-The types of spectroscopy also can be distinguished by the nature of the interaction between the energy and the material. These interactions include:<ref name="Crouch-Skoog-Holler2007">{{cite book |author=Crouch |first1=Stanley R. |url=https://books.google.com/books?id=GrOsQgAACAAJ |title=Principles of instrumental analysis |last2=Skoog |first2=Douglas A. |last3=Holler |first3=F. J. |publisher=Thomson Brooks/Cole |year=2007 |isbn=9780495012016 |location=Australia}}</ref>
+The types of spectroscopy can be distinguished by the nature of the interaction between the energy and the material. These interactions include:<ref name="Crouch-Skoog-Holler2007">{{cite book | title=Principles of instrumental analysis | last1=Crouch | first1=Stanley R. | last2=Skoog | first2=Douglas A. | last3=Holler | first3=F. J. | publisher=Thomson Brooks/Cole | year=2007 | isbn=978-0-495-01201-6 | location=Australia | url=https://books.google.com/books?id=GrOsQgAACAAJ }}</ref>
 * [[Absorption spectroscopy]]: Absorption occurs when energy from the radiative source is absorbed by the material. Absorption is often determined by measuring the fraction of energy transmitted through the material, with absorption decreasing the transmitted portion.
-* [[Emission spectroscopy]]: Emission indicates that radiative energy is released by the material. A material's [[blackbody spectrum]] is a spontaneous emission spectrum determined by its temperature. This feature can be measured in the infrared by instruments such as the atmospheric emitted radiance interferometer.<ref>{{cite journal | last1=Mariani | first1=Z. | last2=Strong | first2=K. | last3=Wolff | first3=M. | last4=Rowe | first4=P. | year=2012 | title=Infrared measurements in the Arctic using two Atmospheric Emitted Radiance Interferometers | journal= Atmospheric Measurement Techniques| volume=5 | issue=2 | pages=329–344 | doi=10.5194/amt-5-329-2012|  last5=Walden | first5=V. | last6=Fogal | first6=P. F. | last7=Duck | first7=T. | last8=Lesins | first8=G. | last9=Turner | first9=D. S. | last10=Cox | first10=C. | last11=Eloranta | first11=E. | last12=Drummond | first12=J. R. | last13=Roy | first13=C.| last14=Turner | first14=D. D. | last15=Hudak | first15=D. | last16=Lindenmaier | first16=I. A. | bibcode=2012AMT.....5..329M| doi-access=free }}</ref> Emission can also be induced by other sources of energy such as [[flame spectroscopy|flames]], [[Spark (fire)|sparks]], [[electric arc]]s or electromagnetic radiation in the case of [[fluorescence spectroscopy|fluorescence]].
+* [[Emission spectroscopy]]: Emission indicates that radiative energy is released by the material. A material's [[blackbody spectrum]] is a spontaneous emission spectrum determined by its temperature. This feature can be measured in the infrared by instruments such as the atmospheric emitted radiance interferometer.<ref>{{cite journal | last1=Mariani | first1=Z. | last2=Strong | first2=K. | last3=Wolff | first3=M. | last4=Rowe | first4=P. | year=2012 | title=Infrared measurements in the Arctic using two Atmospheric Emitted Radiance Interferometers | journal=Atmospheric Measurement Techniques| volume=5 | issue=2 | pages=329–344 | doi=10.5194/amt-5-329-2012|  last5=Walden | first5=V. | last6=Fogal | first6=P. F. | last7=Duck | first7=T. | last8=Lesins | first8=G. | last9=Turner | first9=D. S. | last10=Cox | first10=C. | last11=Eloranta | first11=E. | last12=Drummond | first12=J. R. | last13=Roy | first13=C.| last14=Turner | first14=D. D. | last15=Hudak | first15=D. | last16=Lindenmaier | first16=I. A. | bibcode=2012AMT.....5..329M| doi-access=free }}</ref> Emission can be induced by other sources of energy such as [[flame spectroscopy|flames]], [[Spark (fire)|sparks]], [[electric arc]]s or electromagnetic radiation in the case of [[fluorescence spectroscopy|fluorescence]].
-* [[Elastic scattering]] and [[reflectivity|reflection]] spectroscopy determine how incident radiation is reflected or scattered by a material. [[Crystallography]] employs the scattering of high energy radiation, such as x-rays and electrons, to examine the arrangement of atoms in proteins and solid crystals.
+* [[Elastic scattering]] and [[reflectivity|reflection]] spectroscopy determine how incident radiation is reflected or scattered by a material. [[Crystallography]] employs the scattering of high energy radiation, such as X-rays and electrons, to examine the arrangement of atoms in proteins and solid crystals.
-* [[Impedance spectroscopy]]: Impedance is the ability of a medium to impede or slow the transmittance of energy. For [[optics|optical]] applications, this is characterized by the [[index of refraction]].
+* [[Impedance spectroscopy]], where impedance is the ability of a medium to impede or slow the transmittance of energy. For [[optics|optical]] applications, this is characterized by the [[index of refraction]].
-* [[Inelastic scattering]] phenomena involve an exchange of energy between the radiation and the matter that shifts the wavelength of the scattered radiation. These include [[Raman scattering|Raman]] and [[Compton scattering]].
+* [[Inelastic scattering]] phenomena involve an exchange of energy between X-ray radiation and the matter that shifts the wavelength of the scattered radiation. These include [[Raman scattering|Raman]] and [[Compton scattering]].<ref>{{cite book | last1=Alexandropoulos | first1=N. G. | last2=Theodoridou | first2=I. | year=1988 | chapter=X-Ray Inelastic Scattering Spectroscopy and Its Applications in Solid State Physics | editor1-last=Ferreira | editor1-first=J. G. | editor2-last=Ramos | editor2-first=M. T. | title=X-Ray Spectroscopy in Atomic and Solid State Physics | series=NATO ASI Series | volume=187 | pages=279–299 | publisher=Springer | location=Boston, MA.  | doi=10.1007/978-1-4613-0731-0_13 | isbn=978-1-4612-8054-5 }}</ref>
-* [[Coherent spectroscopy|Coherent]] or resonance spectroscopy are techniques where the radiative energy couples two quantum states of the material in a [[coherence (physics)|coherent]] interaction that is sustained by the radiating field. The coherence can be disrupted by other interactions, such as particle collisions and energy transfer, and so often require high intensity radiation to be sustained. [[Nuclear magnetic resonance spectroscopy|Nuclear magnetic resonance (NMR) spectroscopy]] is a widely used resonance method, and [[ultrafast laser spectroscopy]] is also possible in the infrared and visible spectral regions.
+* [[Coherent spectroscopy|Coherent]] or resonance spectroscopy are techniques where the radiative energy couples two quantum states of the material in a [[coherence (physics)|coherent]] interaction that is sustained by the radiating field. The coherence can be disrupted by other interactions, such as particle collisions and energy transfer, and so often requires high intensity radiation to be sustained. [[Nuclear magnetic resonance spectroscopy|Nuclear magnetic resonance (NMR) spectroscopy]] is a widely used resonance method, and [[ultrafast laser spectroscopy]] is possible in the infrared and visible spectral regions.
 * [[Nuclear spectroscopy]] are methods that use the properties of specific [[Atomic nucleus|nuclei]] to probe the [[local structure]] in matter, mainly [[condensed matter]], [[molecule]]s in liquids or frozen liquids and bio-molecules.
 * [[Quantum logic spectroscopy]] is a general technique used in [[ion traps]] that enables precision spectroscopy of ions with internal structures that preclude [[laser cooling]], state manipulation, and detection. [[Quantum logic]] operations enable a controllable ion to exchange information with a co-trapped ion that has a complex or unknown electronic structure.
 === Type of material ===
-Spectroscopic studies are designed so that the [[radiant energy]] interacts with specific types of matter.
+Spectroscopic studies are designed so that the [[radiant energy]] interacts with specific types of matter. These studies can be divided into three broad categories:<ref>{{cite book | title=Essentials of Chemical Biology: Structures and Dynamics of Biological Macromolecules In Vitro and In Vivo | first1=Andrew D. | last1=Miller | first2=Julian A. | last2=Tanner | edition=2nd | publisher=John Wiley & Sons | year=2024 | page=128 | ISBN=978-1-119-43797-0 | url=https://books.google.com/books?id=Zu3pEAAAQBAJ&pg=PA128 }}</ref> [[electronic spectroscopy]], which measures the transition of electrons between different energy states through absorption or emission of visible or ultraviolet energy; [[vibronic spectroscopy]] of molecules induced by the absorption of infrared energy; and [[rotational spectroscopy]] of molecules caused by microwave energy.<ref>{{cite journal | title=Taking the Pulse of Molecular Rotational Spectroscopy | first=Brooks H. | last=Pate | journal=Science | date=August 19, 2011 | volume=333 | issue=6045 | pages=947–948 | doi=10.1126/science.1207994 }}</ref> The last two can be combined into [[rotational–vibrational spectroscopy]] of a gas.
 ==== Atoms ====
 [[File:Welsbach_Figure_IV_spektroskopische-lytischen-chemie-21.pdf|thumb|Atomic spectra comparison table, from "Spektroskopische Methoden der analytischen Chemie" (1922).]]
-[[Atomic spectroscopy]] was the first application of spectroscopy. [[Atomic absorption spectroscopy]] and [[atomic emission spectroscopy]] involve visible and ultraviolet light. These absorptions and emissions, often referred to as atomic spectral lines, are due to [[Atomic structure#Energy levels|electronic transitions]] of outer shell electrons as they rise and fall from one electron orbit to another. Atoms also have distinct x-ray spectra that are attributable to the excitation of inner shell electrons to excited states.
+[[Atomic spectroscopy]] was the first application of spectroscopy. [[Atomic absorption spectroscopy]] and [[atomic emission spectroscopy]] involve visible and ultraviolet light. These absorptions and emissions, often referred to as atomic spectral lines, are due to [[Atomic structure#Energy levels|electronic transitions]] of outer shell electrons as they rise and fall from one electron orbit to another. Atoms have distinct X-ray spectra that are attributable to the excitation of inner shell electrons to excited states.
-Atoms of different elements have distinct spectra and therefore atomic spectroscopy allows for the identification and quantitation of a sample's elemental composition. After inventing the spectroscope, [[Robert Bunsen]] and [[Gustav Kirchhoff]] discovered new elements by observing their emission spectra. Atomic absorption lines are observed in the solar spectrum and referred to as [[Fraunhofer lines]] after their discoverer. A comprehensive explanation of the [[Hydrogen spectral series|hydrogen spectrum]] was an early success of quantum mechanics and explained the [[Lamb shift]] observed in the hydrogen spectrum, which further led to the development of [[quantum electrodynamics]].
+Atoms of different elements have distinct spectra and therefore atomic spectroscopy allows for the identification and quantitation of a sample's elemental composition. After [[Robert Bunsen]] and [[Gustav Kirchhoff]] invented the spectroscope, Bunsen discovered cesium and rubidium by observing their emission spectra.<ref>{{cite book | title=The Lost Elements: The Periodic Table's Shadow Side | first1=Marco | last1=Fontani | first2=Mariagrazia | last2=Costa | first3=Mary Virginia | last3=Orna | publisher=Oxford University Press | year=2015 | isbn=978-0-19-938334-4 | pages=24–25 | url=https://books.google.com/books?id=Ck9jBAAAQBAJ&pg=PA24 }}</ref> Atomic absorption lines are observed in the solar spectrum and referred to as [[Fraunhofer lines]] after their discoverer.<ref>{{cite journal | title=Fraunhofer and his spectral lines | first=Myles W. | last=Jackson | journal=Annalen der Physik | volume=526 | issue=7-8 | date=August 2014 | pages=A65–A69 | doi=10.1002/andp.201400807 }}</ref> A comprehensive explanation of the [[Hydrogen spectral series|hydrogen spectrum]] was an early success of quantum mechanics<ref>{{cite book | title=The Historical Development of Quantum Theory, Volume 5, Part 2 | first1=Jagdish | last1=Mehra | first2=Helmut | last2=Rechenberg | publisher=Springer Science & Business Media | year=2001 | isbn=978-0-387-95180-5 | pages=459–463 | url=https://books.google.com/books?id=-pL56OcVubgC&pg=PA462 }}</ref> and explained the [[Lamb shift]] observed in the hydrogen spectrum,<ref>{{cite book | chapter=Perturbation Theory in Quantum Mechanics | first1=Luigi E. | last1=Picasso | first2=Luciano | last2=Bracci | first3=Emilio | last3=D'Emilio | title=Mathematics of Complexity and Dynamical Systems | editor-first=Robert A. | editor-last=Meyers | publisher=Springer Science & Business Media | year=2011 | isbn=978-1-4614-1805-4 | page=1352 | chapter-url=https://books.google.com/books?id=iXEmLUcXAPcC&pg=PA1352 }}</ref> which further led to the development of [[quantum electrodynamics]].
-Modern implementations of atomic spectroscopy for studying visible and ultraviolet transitions include [[flame emission spectroscopy]], [[inductively coupled plasma atomic emission spectroscopy]], [[Glow discharge#Use in analytical chemistry|glow discharge spectroscopy]], [[microwave induced plasma]] spectroscopy, and spark or arc emission spectroscopy. Techniques for studying x-ray spectra include [[X-ray spectroscopy]] and [[X-ray fluorescence]].
+Modern implementations of atomic spectroscopy for studying visible and ultraviolet transitions include [[flame emission spectroscopy]], [[inductively coupled plasma atomic emission spectroscopy]],<ref>{{cite book | title=Basic Concepts Of Analytical Chemistry | first=S. M. | last=Khopkar | publisher=New Age International | year=1998 | isbn=978-81-224-1159-1 | pages=284–292 | url=https://books.google.com/books?id=e8Ju_n8DN1sC&pg=PA284 }}</ref> [[Glow discharge#Use in analytical chemistry|glow discharge spectroscopy]],<ref>{{cite journal | title=Glow discharge mass spectrometry | first1=W. W. | last1=Harrison | first2=K. R. | last2=Hess | first3=R. K. | last3=Marcus | first4=F. L. | last4=King | journal=Analytical Chemistry | volume=58 | issue=2 | pages=341A–356A | publisher=American Chemical Society | doi=10.1021/ac00293a002 }}</ref> [[microwave induced plasma]] spectroscopy,<ref>{{cite journal | title=Microwave-induced plasma–optical emission spectrometry – fundamental aspects and applications in metal speciation analysis | first1=B. | last1=Rosenkranz | first2=J. | last2=Bettmer | journal=TrAC Trends in Analytical Chemistry | volume=19 | issue=2–3 | date=February–March 2000 | pages=138-156 | doi=10.1016/S0165-9936(99)00189-2 }}</ref> and spark or arc emission spectroscopy.<ref>{{cite journal | first1=B. | last1=Vayner | first2=D. C. | last2=Ferguson | first3=J. T. | last3=Galofaro | title=Emission Spectra of Arc Plasmas | journal=IEEE Transactions on Plasma Science | volume=36 | issue=5 | pages=2219–2227 | date=October 2008 | doi=10.1109/TPS.2008.2001424 }}</ref> Techniques for studying X-ray spectra include [[X-ray spectroscopy]]<ref name=Hippert_et_al_eds_2005/> and [[X-ray fluorescence]].<ref>{{cite book | chapter=Elemental Analysis by X-Ray Fluorescence Spectroscopy | first1=A. D. | last1=Karathanasis | first2=B. F. | last2=Hajek | editor1-first=D. L. | editor1-last=Sparks | editor2-first=A. L. | editor2-last=Page | editor3-first=P. A. | editor3-last=Helmke | editor4-first=R. H. | editor4-last=Loeppert | editor5-first=P. N. | editor5-last=Soltanpour | editor6-first=M. A. | editor6-last=Tabatabai | editor7-first=C. T. | editor7-last=Johnston | editor8-first=M. E. | editor8-last=Sumner | title=Methods of Soil Analysis: Part 3 Chemical Methods | series=SSSA Book Series | date=January 1996 | isbn=978-0-89118-825-4 | doi=10.2136/sssabookser5.3.c7 }}</ref>
 ==== Molecules ====
-The combination of atoms into molecules leads to the creation of unique types of energetic states and therefore unique spectra of the transitions between these states. Molecular spectra can be obtained due to electron spin states ([[electron paramagnetic resonance]]), [[rotational spectroscopy|molecular rotations]], [[molecular vibration]], and electronic states. Rotations are collective motions of the atomic nuclei and typically lead to spectra in the microwave and millimetre-wave spectral regions. Rotational spectroscopy and microwave spectroscopy are synonymous. Vibrations are relative motions of the atomic nuclei and are studied by both infrared and [[Raman spectroscopy]]. Electronic excitations are studied using visible and ultraviolet spectroscopy as well as [[fluorescence spectroscopy]].<ref name="Crouch-Skoog-Holler2007" /><ref>{{Cite book |last=Kroto |first=H. W. |url=https://books.google.com/books?id=Nu8NAQAAIAAJ |title=Molecular Rotation Spectra |date=1975 |publisher=Wiley |isbn=9780471508533 |oclc=793428}}</ref><ref>Philip R. Bunker and Per Jensen (1998),''Molecular Symmetry and Spectroscopy'', 2nd ed.  NRC Research Press, Ottawa [https://volumesdirect.com/products/molecular-symmetry-and-spectroscopy?_pos=1&_sid=ed0cc0319&_ss=r] {{ISBN|9780660196282}}</ref><ref>{{Cite book |last1=Papoušek |first1=Dušan |last2=Aliev |first2=Mamed Ragimovich |url=https://books.google.com/books?id=fb7vAAAAMAAJ |title=Molecular Vibrational-rotational Spectra: Theory and Applications of High Resolution Infrared, Microwave, and Raman Spectroscopy of Polyatomic Molecules |date=1982 |publisher=Elsevier Scientific Publishing Company |isbn=9780444997371 |location=Amsterdam |oclc=7278301}}</ref><ref>{{Cite book |last1=Wilson |first1=Edgar B. |url=https://books.google.com/books?id=CPkvsDrPiv0C |title=Molecular Vibrations: The Theory of Infrared and Raman Vibrational Spectra |last2=Decius |first2=John C. |last3=Cross |first3=Paul C. |date=1980-03-01 |publisher=Courier Corporation |isbn=9780486639413 |oclc=1023249001}}</ref>
+The combination of atoms into molecules leads to the creation of unique types of energetic states and therefore unique spectra of the transitions between these states. Molecular spectra can be obtained due to electron spin states ([[electron paramagnetic resonance]]), [[rotational spectroscopy|molecular rotations]], [[molecular vibration]], and electronic states. Rotations are collective motions of the atomic nuclei and typically lead to spectra in the microwave and millimetre-wave spectral regions. Rotational spectroscopy and microwave spectroscopy are synonymous. Vibrations are relative motions of the atomic nuclei and are studied by both infrared and [[Raman spectroscopy]]. Electronic excitations are studied using visible and ultraviolet spectroscopy as well as [[fluorescence spectroscopy]].<ref name="Crouch-Skoog-Holler2007" /><ref>{{Cite book |last=Kroto |first=H. W. |url=https://books.google.com/books?id=Nu8NAQAAIAAJ |title=Molecular Rotation Spectra |date=1975 |publisher=Wiley |isbn=978-0-471-50853-3 |oclc=793428}}</ref><ref>{{cite book | first1=Philip R. | last1=Bunker | first2=Per | last2=Jensen | year=1998 | title=Molecular Symmetry and Spectroscopy | edition=2nd | publisher=NRC Research Press | location=Ottawa | url=https://volumesdirect.com/products/molecular-symmetry-and-spectroscopy?_pos=1&_sid=ed0cc0319&_ss=r | isbn=9780660196282 }}</ref><ref>{{Cite book |last1=Papoušek |first1=Dušan |last2=Aliev |first2=Mamed Ragimovich |url=https://books.google.com/books?id=fb7vAAAAMAAJ |title=Molecular Vibrational-rotational Spectra: Theory and Applications of High Resolution Infrared, Microwave, and Raman Spectroscopy of Polyatomic Molecules |date=1982 |publisher=Elsevier Scientific Publishing Company |isbn=978-0-444-99737-1 |location=Amsterdam |oclc=7278301}}</ref><ref>{{Cite book |last1=Wilson |first1=Edgar B. |url=https://books.google.com/books?id=CPkvsDrPiv0C |title=Molecular Vibrations: The Theory of Infrared and Raman Vibrational Spectra |last2=Decius |first2=John C. |last3=Cross |first3=Paul C. |date=1980-03-01 |publisher=Courier Corporation |isbn=978-0-486-63941-3 |oclc=1023249001}}</ref>
 Studies in molecular spectroscopy led to the development of the first [[maser]] and contributed to the subsequent development of the [[laser]].
 ==== Crystals and extended materials ====
-The combination of atoms or molecules into crystals or other extended forms leads to the creation of additional energetic states. These states are numerous and therefore have a high density of states. This high density often makes the spectra weaker and less distinct, i.e., broader. For instance, blackbody radiation is due to the thermal motions of atoms and molecules within a material. Acoustic and mechanical responses are due to collective motions as well.
+The combination of atoms or molecules into crystals or other extended forms leads to the creation of additional energetic states. These states are numerous and therefore have a high density of states. This high density often makes the spectra weaker and less distinct, i.e., broader.{{cn|date=December 2025}} For instance, blackbody radiation is due to the thermal motions of atoms and molecules within a material. Acoustic and mechanical responses are due to collective motions as well.{{cn|date=December 2025}} Pure crystals, though, can have distinct spectral transitions, and the crystal arrangement has an effect on the observed molecular spectra. The regular [[lattice structure]] of crystals scatters X-rays,<ref>{{cite journal | title=X Ray crystallography | first1=M. S. | last1=Smyth | first2=J. H. J. | last2=Martin | journal=Molecular Pathology | date=February 2000 | volume=53 | issue=1 | pages=8–14 | doi=10.1136/mp.53.1.8 | doi-access=free | pmc=1186895 | pmid=10884915 }}</ref> electrons,<ref>{{cite journal | title=Electron crystallography | first=D. L. | last=Dorset | journal=Acta Crystallographica Section B | year=1996 | volume=B52 | pages=753–769 | doi=10.1107/S0108768196005599 }}</ref> or neutrons,<ref>{{cite journal | title=Neutron crystallography: opportunities, challenges, and limitations | first1=Matthew P. | last1=Blakeley | first2=Paul | last2=Langan | first3=Nobuo | last3=Niimura | first4=Alberto | last4=Podjarny | journal=Current Opinion in Structural Biology | volume=18 | issue=5 | date=October 2008 | pages=593–600 | doi=10.1016/j.sbi.2008.06.009 }}</ref> allowing for crystallographic studies.
-Pure crystals, though, can have distinct spectral transitions, and the crystal arrangement also has an effect on the observed molecular spectra. The regular [[lattice structure]] of crystals also scatters x-rays, electrons or neutrons allowing for crystallographic studies.
 ==== Nuclei ====
-Nuclei also have distinct energy states that are widely separated and lead to [[gamma ray]] spectra. Distinct nuclear spin states can have their energy separated by a magnetic field, and this allows for [[nuclear magnetic resonance spectroscopy]].
+Nuclei have distinct energy states that are widely separated and lead to [[gamma ray]] spectra.{{cn|date=December 2025}} Distinct nuclear spin states can have their energy separated by a magnetic field, and this allows for [[nuclear magnetic resonance spectroscopy]].<ref>{{cite web | title=Understanding NMR Spectroscopy | first=James | last=Keeler | publisher=University of Cambridge | url=https://www-keeler.ch.cam.ac.uk/lectures/Irvine/ | access-date=2025-12-12 }}</ref>
 == Other types ==
 {{Prose|section|date=April 2016}}
 Other types of spectroscopy are distinguished by specific applications or implementations:
-* [[Acoustic resonance spectroscopy]] is based on sound waves primarily in the [[Sound|audible]] and [[Ultrasound|ultrasonic]] regions.
+* [[Acoustic resonance spectroscopy]] is based on sound waves primarily in the [[Sound|audible]] and [[Ultrasound|ultrasonic]] regions.<ref>{{cite journal | last1=Ripoche | first1=J. | last2=Maze | first2=G. | last3=Izbicki | first3=JL | title=A new acoustic spectroscopy: Resonance spectroscopy by the MIIR | journal=Journal of Nondestructive Evaluation | volume=5 | pages=69–79 | year=1985 | doi=10.1007/BF00566957 }}</ref>
-* [[Auger electron spectroscopy]] is a method used to study surfaces of materials on a micro-scale.  It is often used in connection with electron microscopy.
+* [[Auger electron spectroscopy]] is a method used to study surfaces of materials on a micro-scale.  It is often used in connection with electron microscopy.<ref>{{cite book | last1=Gunawardane | first1=R. P. | last2=Arumainayagam | first2=C. R. | year=2006 | chapter=Auger Electron Spectroscopy | editor-last=Vij | editor-first=D. | title=Handbook of Applied Solid State Spectroscopy | publisher=Springer | location=Boston, MA. | doi=10.1007/0-387-37590-2_10 }}</ref>
-* [[Cavity ring-down spectroscopy]]
+* [[Cavity ring-down spectroscopy]] enables measurement of absolute [[optical extinction]] by samples that [[scattering|scatter]] and [[Absorption (electromagnetic radiation)|absorb]] light.<ref>{{cite book | chapter=An Introduction to Cavity Ring-Down Spectroscopy | first1=Kevin K. | last1=Lehmann | first2=Giel | last2=Berden | first3=Richard | last3=Engeln | title=Cavity Ring-Down Spectroscopy: Techniques and Applications | editor1-first=Giel | editor1-last=Berden | editor2-first=Richard | editor2-last=Engeln | publisher=John Wiley & Sons | year=2009 | isbn=978-1-4443-0824-2 | pages=1–3 | chapter-url=https://books.google.com/books?id=5jQM88VYwzQC&pg=PA1 }}</ref>
-* [[Circular dichroism]] spectroscopy
+* [[Circular dichroism]] spectroscopy measures the differential absorption of left- and right-handed [[Circular polarization|circularly polarized]] light.<ref>{{cite book | last1=Hoffmann | first1=S. V. | last2=Fano | first2=M. | last3=van de Weert | first3=M. | year=2016 | chapter=Circular Dichroism Spectroscopy for Structural Characterization of Proteins | editor1-last=Müllertz | editor1-first=A. | editor2-last=Perrie | editor2-first=Y. | editor3-last=Rades | editor3-first=T. | title=Analytical Techniques in the Pharmaceutical Sciences | series=Advances in Delivery Science and Technology | publisher=Springer | location=New York, NY. | doi=10.1007/978-1-4939-4029-5_6 }}</ref>
-* [[Coherent anti-Stokes Raman spectroscopy]] is a recent technique that has high sensitivity and powerful applications for ''in vivo'' spectroscopy and imaging.<ref>{{cite journal | last1=Evans | first1=C. L. | last2=Xie | first2=X. S. | date=2008 | title=Coherent Anti-Stokes Raman Scattering Microscopy: Chemical Imaging for Biology and Medicine | journal=[[Annual Review of Analytical Chemistry]] | volume=1 | pages=883–909 | doi=10.1146/annurev.anchem.1.031207.112754 | pmid=20636101 | bibcode=2008ARAC....1..883E}}</ref>
+* [[Coherent anti-Stokes Raman spectroscopy]] is a recent technique that has high sensitivity and powerful applications for ''in vivo'' spectroscopy and imaging.<ref>{{cite journal | last1=Evans | first1=C. L. | last2=Xie | first2=X. S. | date=2008 | title=Coherent Anti-Stokes Raman Scattering Microscopy: Chemical Imaging for Biology and Medicine | journal=[[Annual Review of Analytical Chemistry]] | volume=1 | pages=883–909 | doi=10.1146/annurev.anchem.1.031207.112754 | pmid=20636101 | bibcode=2008ARAC....1..883E | url=http://nrs.harvard.edu/urn-3:HUL.InstRepos:33471118 }}</ref>
-* [[Cold vapour atomic fluorescence spectroscopy]]
+* [[Cold vapour atomic fluorescence spectroscopy]] is a subclass of the [[atomic emission spectroscopy]] technique that measures trace amounts of volatile heavy metals in the air, such as mercury.<ref>{{cite journal | last1=Kopysc | first1=Edyta | last2=Pyrzynska | first2=Krystyna | last3=Garbos | first3=Slawomir | last4=Bulska | first4=Ewa | title=Determination of Mercury by Cold-Vapor Atomic AbsorptionSpectrometry with Preconcentration on a Gold-Trap | journal=Analytical Sciences | date=December 17, 2000 | volume=16 | pages=1309–1312 | doi=10.2116/analsci.16.1309|doi-access=free}}</ref>
-* [[Two-dimensional nuclear magnetic resonance spectroscopy#Correlation spectroscopy (COSY)|Correlation spectroscopy]] encompasses several types of two-dimensional NMR spectroscopy.
+* [[Two-dimensional nuclear magnetic resonance spectroscopy#Correlation spectroscopy (COSY)|Correlation spectroscopy]] encompasses several types of two-dimensional NMR spectroscopy.<ref>{{cite journal | title=Advances in two-dimensional correlation spectroscopy | first=Isao | last=Noda | journal=Vibrational Spectroscopy | volume=36 | issue=2 | year=2004 | pages=143–165 | doi=10.1016/j.vibspec.2003.12.016 }}</ref>
-* [[Deep-level transient spectroscopy]] measures concentration and analyzes parameters of electrically active defects in [[semiconductor|semiconducting]] materials.
+* [[Deep-level transient spectroscopy]] measures concentration and analyzes parameters of electrically active defects in [[semiconductor|semiconducting]] materials.<ref>{{cite journal | title=Defect identification based on first-principles calculations for deep level transient spectroscopy | first1=Darshana | last1=Wickramaratne | first2=Cyrus E. | last2=Dreyer | first3=Bartomeu | last3=Monserrat | first4=Jimmy-Xuan | last4=Shen | first5=John L. | last5=Lyons | first6=Audrius | last6=Alkauskas | first7=Chris G. | last7=Van de Walle | journal=Applied Physics Letters | volume=113 | article-number=192106 | year=2018 | doi=10.1063/1.5047808 }}</ref>
-* [[Dielectric spectroscopy]]
+* [[Dielectric spectroscopy]] measures the [[dielectric]] properties of a medium as a function of [[frequency]].<ref>{{cite journal | last1=Volkov | first1=A. A. | last2=Prokhorov | first2=A. S. | title=Broadband Dielectric Spectroscopy of Solids | journal=Radiophysics and Quantum Electronics | volume=46 | pages=657–665 | year=2003 | doi=10.1023/B:RAQE.0000024994.15881.c9 }}</ref>
-* [[Dual-polarization interferometry]] measures the real and imaginary components of the complex refractive index.
+* [[Dual-polarization interferometry]] measures the real and imaginary components of the complex refractive index.<ref>{{cite journal | title=Dual-Polarization Interferometry: A Novel Technique To Light up the Nanomolecular World | journal=Chemical Reviews | volume=115 | issue=1 | pages=265–294 | date=December 2, 2014 | first1=Jorge | last1=Escorihuela | first2=Miguel Ángel | last2=González-Martínez | first3=José Luis | last3=López-Paz | first4=Rosa | last4=Puchades | first5=Ángel | last5=Maquieira | first6=David | last6=Gimenez-Romero | series=ACS Publications | doi=10.1021/cr5002063 }}</ref>
-* [[Electron energy loss spectroscopy]] in transmission electron microscopy.
+* [[Electron energy loss spectroscopy]] in transmission electron microscopy.<ref>{{cite conference | title=Fundamentals of electron energy-loss spectroscopy | first1=F. | last1=Hofer | first2=F. P. | last2=Schmidt | first3=W. | last3=Grogger | first4=G. | last4=Kothleitner | series=IOP Conference Series: Materials Science and Engineering | volume=109 | conference=14th European Workshop on Modern Developments and Applications in Microbeam Analysis (EMAS 2015 Workshop) 3–7 May 2015, Portorož, Slovenia | doi=10.1088/1757-899X/109/1/012007 }}</ref>
-* [[Electron phenomenological spectroscopy]] measures the physicochemical properties and characteristics of the electronic structure of multicomponent and complex molecular systems.
+* [[Electron phenomenological spectroscopy]] measures the [[Physical chemistry|physicochemical]] properties and characteristics of the electronic structure of multicomponent and complex molecular systems.<ref>{{cite journal | last1=Dolomatov | first1=M. Y. | last2=Subkhankulov | first2=V. R. | last3=Dolomatova | first3=M. M. | first4=E. A. | last4=Kovaleva | first5=S. S. | last5=Vershinin | first6=O. A. | last6=Belotelov | first7=I. V. | last7=Kazaev | title=Use of Electron Phenomenological Spectroscopy for the Rapid Determination of the Properties of Raw Material for the Preparation of Multifunctional Carbon Materials | journal=Chemistry and Technology of Fuels and Oils | volume=61 | pages=340–345 | year=2025 | doi=10.1007/s10553-025-01872-5 }}</ref>
-* [[Electron paramagnetic resonance]] spectroscopy
+* [[Electron paramagnetic resonance]] spectroscopy is similar to [[nuclear magnetic resonance]] (NMR), except it measures the [[Spin (physics)|spin]] excitement of [[unpaired electron]]s.<ref>{{cite journal | last=Lancaster | first=G. | title=Electron paramagnetic resonance (a review) | journal=Journal of Materials Science | volume=2 | pages=489–495 | year=1967 | doi=10.1007/BF00562955 }}</ref>
-* [[Force spectroscopy]]
+* [[Force spectroscopy]] is a set of techniques for the study of the interactions and the binding forces between individual molecules, although the name is somewhat misleading because there is no true matter-radiation interaction.<ref>{{cite journal | title=Force Spectroscopy and Beyond: Innovations and Opportunities | first1=Bhavik | last1=Nathwani | first2=William M. | last2=Shih | first3=Wesley P. | last3=Wong | journal=Biophysical Perspective | volume=115 | issue=12 | pages=2279–2285 | date=December 18, 2018 | pmid=30447991 | pmc=6302248 | doi=10.1016/j.bpj.2018.10.021 }}</ref>
-* [[Fourier-transform spectroscopy]] is an efficient method for processing spectra data obtained using interferometers. [[Fourier-transform infrared spectroscopy]] is a common implementation of infrared spectroscopy. NMR also employs [[Fourier transform]]s.
+* [[Fourier-transform spectroscopy]] is an efficient method for processing spectra data obtained using interferometers. [[Fourier-transform infrared spectroscopy]] is an implementation of infrared spectroscopy.<ref>{{cite book | last=Faix | first=O. | year=1992 | chapter=Fourier Transform Infrared Spectroscopy | editor1-last=Lin | editor1-first=S. Y. | editor2-last=Dence
-* [[Gamma spectroscopy]]
+| editor2-first=C.W. | title=Methods in Lignin Chemistry | series=Springer Series in Wood Science | publisher=Springer | location=Berlin, Heidelberg | doi=10.1007/978-3-642-74065-7_7 }}</ref> NMR also employs [[Fourier transform]]s.
+* [[Gamma spectroscopy]] measures the [[gamma ray]] emissions from high energy processes including [[radioactive source|radioactive]] and astrophysical sources.<ref>{{cite web | title=Gamma-ray spectrometers | publisher=Space Science Institute | url=https://space-science.llnl.gov/research/gamma-ray-spectrometers | access-date=2025-12-29 }}</ref>
 * [[Hadron spectroscopy]] studies the energy/mass spectrum of hadrons according to [[Spin (physics)|spin]], [[parity (physics)|parity]], and other particle properties. Baryon spectroscopy and meson spectroscopy are types of hadron spectroscopy.
-* [[Multispectral imaging]] and [[hyperspectral imaging]] is a method to create a complete picture of the environment or various objects, each pixel containing a full visible, visible near infrared, near infrared, or infrared spectrum.
+* [[Multispectral imaging]] and [[hyperspectral imaging]] is a method to create a complete picture of the environment or various objects, each pixel containing a full visible, visible near infrared, near infrared, or infrared spectrum.<ref>{{cite journal | title=Advances in Spectral Imaging: A Review of Techniques and Technologies | first1=Sani | last1=Mukhtar | first2=Amir | last2=Arbabi | first3=Jaime | last3=Viegas | journal=IEEE Access | volume=13 | pages=35848–35902 | year=2025 | doi=10.1109/ACCESS.2025.3544476 }}</ref>
-* [[Inelastic electron tunneling spectroscopy]] uses the changes in current due to inelastic electron-vibration interaction at specific energies that can also measure optically forbidden transitions.
+* [[Inelastic electron tunneling spectroscopy]] uses the changes in current due to inelastic electron-vibration interaction at specific energies that can also measure optically forbidden transitions.<ref>{{cite journal | title=Inelastic Electron Tunneling Spectroscopy | first1=S. K. | last1=Khanna | first2=John | last2=Lambe | journal=Science | date=June 24, 1983 | volume=220 | issue=4604 | pages=1345–1351 | doi=10.1126/science.220.4604.1345 }}</ref>
 * [[Inelastic neutron scattering]] is similar to Raman spectroscopy, but uses neutrons instead of photons.
 * [[Laser-induced breakdown spectroscopy]], also called laser-induced plasma spectrometry
-* Laser spectroscopy uses [[tunable laser]]s<ref>[[W. Demtröder]], ''Laser Spectroscopy'', 3rd Ed. (Springer, 2003).</ref> and other types of coherent emission sources, such as optical parametric oscillators,<ref>{{cite book | editor=F. J. Duarte | editor-link=F. J. Duarte | title=Tunable Laser Applications | edition=3rd | publisher=[[CRC Press]] | location=Boca Raton | year=2016 | isbn=978-1-4822-6106-6 | author1=Brian Orr | author2=J. G. Haub | author3=Y. He | author4=R. T. White | chapter=Spectroscopic Applications of Pulsed Tunable Optical Parametric Oscillators | pages=17–142| author1-link=Brian Orr }}</ref> for selective excitation of atomic or molecular species.
+* Laser spectroscopy uses [[tunable laser]]s<ref>{{cite book | first=W. | last=Demtröder | author-link=W. Demtröder | title=Laser Spectroscopy | edition=4th | publisher=Springer Science & Business Media | year=2008 | page=314 | isbn=978-3-540-73418-5 | url=https://books.google.com/books?id=5vuqvvb9YxkC&pg=PA314 }}</ref>  and other types of coherent emission sources, such as [[Optical parametric oscillator|optical parametric oscillators]],<ref>{{cite book | editor-first=F. J. | editor-last=Duarte | editor-link=F. J. Duarte | title=Tunable Laser Applications | edition=3rd | publisher=[[CRC Press]] | location=Boca Raton | year=2016 | isbn=978-1-4822-6106-6 | first1=Brian | last1=Orr | first2=J. G. | last2=Haub | first3=Y. | last3=He | first4=R. T. | last4=White | chapter=Spectroscopic Applications of Pulsed Tunable Optical Parametric Oscillators | pages=17–142| author1-link=Brian Orr }}</ref> for selective excitation of atomic or molecular species.
-* [[Light Scattering Spectroscopy|Light scattering spectroscopy]] (LSS) is a spectroscopic technique typically used to evaluate morphological changes in [[Epithelium|epithelial cells]] in order to study [[Mucous membrane|mucosal tissue]] and detect early [[cancer]] and [[Precancerous condition|precancer]].<ref name="link.aps.org"/><ref>{{Cite journal |last1=Backman |first1=V. |last2=Wallace |first2=M. B. |last3=Perelman |first3=L. T. |last4=Arendt |first4=J. T. |last5=Gurjar |first5=R. |last6=Müller |first6=M. G. |last7=Zhang |first7=Q. |last8=Zonios |first8=G. |last9=Kline |first9=E. |last10=McGillican |first10=T. |last11=Shapshay |first11=S. |last12=Valdez |first12=T. |last13=Badizadegan |first13=K. |last14=Crawford |first14=J. M. |last15=Fitzmaurice |first15=M. |date=July 2000 |title=Detection of preinvasive cancer cells |url=https://www.nature.com/articles/35017638 |journal=Nature |language=en |volume=406 |issue=6791 |pages=35–36 |doi=10.1038/35017638 |pmid=10894529 |s2cid=4383575 |issn=1476-4687|url-access=subscription }}</ref>
+* [[Light Scattering Spectroscopy|Light scattering spectroscopy]] (LSS) is a spectroscopic technique typically used to evaluate morphological changes in [[Epithelium|epithelial cells]] in order to study [[Mucous membrane|mucosal tissue]] and detect early [[cancer]] and [[Precancerous condition|precancer]].<ref name="link.aps.org"/><ref>{{Cite journal |last1=Backman |first1=V. |last2=Wallace |first2=M. B. |last3=Perelman |first3=L. T. |last4=Arendt |first4=J. T. |last5=Gurjar |first5=R. |last6=Müller |first6=M. G. |last7=Zhang |first7=Q. |last8=Zonios |first8=G. |last9=Kline |first9=E. |last10=McGillican |first10=T. |last11=Shapshay |first11=S. |last12=Valdez |first12=T. |last13=Badizadegan |first13=K. |last14=Crawford |first14=J. M. |last15=Fitzmaurice |first15=M. |date=July 2000 |title=Detection of preinvasive cancer cells |url=https://www.nature.com/articles/35017638 |journal=Nature |language=en |volume=406 |issue=6791 |pages=35–36 |doi=10.1038/35017638 |pmid=10894529 |bibcode=2000Natur.406...35B |s2cid=4383575 |issn=1476-4687|url-access=subscription }}</ref>
 * Mass spectroscopy is a historical term used to refer to [[mass spectrometry]]. The current recommendation is to use the latter term.<ref>{{cite journal | last1=Murray | first1=Kermit K. | last2=Boyd | first2=Robert K. | last3=Eberlin | first3=Marcos N. | last4=Langley | first4=G. John | last5=Li | first5=Liang | last6=Naito | first6=Yasuhide | title=Definitions of terms relating to mass spectrometry (IUPAC Recommendations 2013) | journal=[[Pure and Applied Chemistry]] | year=2013 | page=1 | issn=0033-4545 | doi=10.1351/PAC-REC-06-04-06 | volume=85 | issue=7 | url=http://www.degruyter.com/downloadpdf/j/pac.2013.85.issue-7/pac-rec-06-04-06/pac-rec-06-04-06.xml| doi-access=free }}</ref> The term "mass spectroscopy" originated in the use of [[phosphor]] screens to detect ions.
-* [[Mössbauer spectroscopy]] probes the properties of specific [[isotope|isotopic]] [[Atomic nucleus|nuclei]] in different atomic environments by analyzing the resonant absorption of [[gamma ray]]s. See also [[Mössbauer effect]].
+* [[Mössbauer spectroscopy]] probes the properties of specific [[isotope|isotopic]] [[Atomic nucleus|nuclei]] in different atomic environments by analyzing the resonant absorption of [[gamma ray]]s. See [[Mössbauer effect]].
 * [[Multivariate optical computing]] is an all optical [[compressed sensing]] technique, generally used in harsh environments, that directly calculates chemical information from a spectrum as analogue output.
 * [[Neutron spin echo]] spectroscopy measures internal dynamics in proteins and other [[soft matter]] systems.
 * [[Nuclear quadrupole resonance]] is a chemical spectroscopy method mediated by NMR of the [[electric field gradient]] (EFG) in the absence of magnetic field
 * [[Perturbed angular correlation]] (PAC) uses radioactive nuclei as probe to study electric and magnetic fields ([[hyperfine structure|hyperfine interactions]]) in crystals ([[condensed matter]]) and bio-molecules.
-* [[Photoacoustic spectroscopy]] measures the sound waves produced upon the absorption of radiation.
+* [[Photoacoustic spectroscopy]] is the measurement of the effect of absorbed electromagnetic energy on matter by means of acoustic detection.<ref>{{cite web | title=Photoacoustic Spectroscopy | website=Spectroscopy Online | first=David W. | last=Ball | date=September 2006 | volume=21 | issue=9 | url=https://www.spectroscopyonline.com/view/photoacoustic-spectroscopy | access-date=2025-11-25 }}</ref>
-* [[Photoemission spectroscopy]]
+* Acoustic emission spectroscopy is the measurement of acoustic waves as a material is deformed.<ref>{{cite journal | title=Acoustic Emission Spectroscopy: Applications in Geomaterials and Related Materials | first1=Ekhard K. H. | last1=Salje | first2=Xiang | last2=Jiang | first3=Jack | last3=Eckstein | first4=Lei | last4=Wang | journal=Applied Sciences | year=2021 | volume=11 | issue=19 | page=8801 | doi=10.3390/app11198801 | doi-access=free }}</ref>
+* [[Photoemission spectroscopy]] measures the energy or spin of electrons emitted from materials by the [[photoelectric effect]].<ref>{{cite journal | title=Photoelectron spectroscopy—An overview | first1=Stefan | last1=Hüfner | first2=Stefan | last2=Schmidt | first3=Friedrich | last3=Reinert | journal=Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment | volume=547 | issue=1 | date=July 21, 2005 | pages=8–23 | publisher=Elsevier | doi=10.1016/j.nima.2005.05.008 }}</ref>
 * [[Photothermal spectroscopy]] measures heat evolved upon absorption of radiation.
 * [[Femtochemistry#Pump-probe spectroscopy|Pump-probe spectroscopy]] can use ultrafast laser pulses to measure [[reaction intermediate]]s in the femtosecond timescale.
 * [[Raman optical activity]] spectroscopy exploits Raman scattering and optical activity effects to reveal detailed information on chiral centers in molecules.
-* [[Raman spectroscopy]]
+* [[Raman spectroscopy]] is used to determine vibrational modes of molecules, providing a structural fingerprint by which molecules can be identified.<ref>{{cite journal | title=Chemical Applications of Raman Spectroscopy | first=Bernhard | last=Schrader | journal=Angewandte Chemie | volume=12 | issue=11 | date=November 1973 | pages=884–908 | doi=10.1002/anie.197308841 }}</ref>
 * [[Saturated spectroscopy]]
 * [[Scanning tunneling spectroscopy]]
 * [[Spectrophotometry]]
-* Spin noise spectroscopy traces spontaneous fluctuations of electronic and nuclear spins.<ref>{{cite journal | doi=10.1088/0034-4885/79/10/106501 | pmid=27615689 | title=The theory of spin noise spectroscopy: a review | journal=[[Reports on Progress in Physics]] | volume=79 | issue=10 | page=106501 | year=2016 | author1=N. A. Sinitsyn | author2=Y. V. Pershin | bibcode=2016RPPh...79j6501S | arxiv=1603.06858| s2cid=4393400 }}</ref>
+* Spin noise spectroscopy traces spontaneous fluctuations of electronic and nuclear spins.<ref>{{cite journal | doi=10.1088/0034-4885/79/10/106501 | pmid=27615689 | title=The theory of spin noise spectroscopy: a review | journal=[[Reports on Progress in Physics]] | volume=79 | issue=10 | article-number=106501 | year=2016 | first1=N. A. | last1=Sinitsyn | first2=Y. V. | last2=Pershin | bibcode=2016RPPh...79j6501S | arxiv=1603.06858| s2cid=4393400 }}</ref>
 * [[Time-resolved spectroscopy]] measures the decay rates of excited states using various spectroscopic methods.
 * [[Time stretch analog-to-digital converter|Time-stretch]] spectroscopy<ref>{{cite journal | pages=48–51 | doi=10.1038/nphoton.2007.253 | title=Amplified wavelength–time transformation for real-time spectroscopy | journal=[[Nature Photonics]] | volume=2 | issue=1 | year=2008 | last1=Solli | first1=D. R. | last2=Chou | first2=J. | last3=Jalali | first3=B. | bibcode=2008NaPho...2...48S}}</ref><ref>{{cite journal | doi=10.1063/1.2896652 | title=Real-time spectroscopy with subgigahertz resolution using amplified dispersive Fourier transformation | journal=[[Applied Physics Letters]] | volume=92 | issue=11 | page=111102 | year=2008 | last1=Chou | first1=Jason | last2=Solli | first2=Daniel R.| last3=Jalali | first3=Bahram | bibcode=2008ApPhL..92k1102C | arxiv=0803.1654| s2cid=53056467 }}</ref>
@@ Line 122: / Line 130: @@
 == Applications ==
-[[File:UVES on UT2-KUEYEN.jpg|thumb|UVES is a high-resolution spectrograph on the [[Very Large Telescope]].<ref>{{cite news|title=Media advisory: Press Conference to Announce Major Result from Brazilian Astronomers|url=http://www.eso.org/public/announcements/ann13066/|access-date=21 August 2013|newspaper=ESO Announcement}}</ref> ]]
+[[File:UVES on UT2-KUEYEN.jpg|thumb|UVES is a high-resolution spectrograph on the [[Very Large Telescope]].<ref>{{cite news | title=Media advisory: Press Conference to Announce Major Result from Brazilian Astronomers | date=20 August 2013 | url=http://www.eso.org/public/announcements/ann13066/ | access-date=21 August 2013 | newspaper=ESO Announcement | publisher=The European Southern Observatory }}</ref> ]]
-There are several applications of spectroscopy in the fields of medicine, physics, chemistry, and astronomy.  Taking advantage of the properties of [[absorbance]] and with [[astronomy emission]], spectroscopy can be used to identify certain states of nature.  The uses of spectroscopy in so many different fields and for so many different applications has caused specialty scientific subfields. Such examples include:
+There are several applications of spectroscopy in the fields of medicine, physics, chemistry, and astronomy.  Taking advantage of the properties of [[absorbance]] and, with astronomy, [[Emission spectrum|emission]], spectroscopy can be used to identify certain states of nature.  The uses of spectroscopy in so many different fields and for so many different applications has caused specialty scientific subfields. Such examples include:
 * Determining the atomic structure of a sample<ref name="Bowers">
   {{cite book
    | title = Sir Charles Wheatstone FRS: 1802–1875
    | edition = 2nd
-   | author = Brian Bowers
+   | first = Brian | last=Bowers
    | publisher = IET
    | date = 2001
@@ Line 138: / Line 146: @@
 * Studying spectral emission lines of the sun and distant galaxies<ref name="Brand 57">
   {{cite book
+ | chapter=Emission and Absorption, ca. 1800–1870
    | title = Lines of Light: The Sources of Dispersive Spectroscopy, 1800 – 1930
    | last = Brand
@@ Line 143: / Line 152: @@
    | publisher = Gordon and Breach Publishers
    | date = 1995
-   | isbn = 978-2884491624
+   | isbn = 978-2-88449-162-4
    | page = 57
+ | chapter-url=https://books.google.com/books?id=spYSK-g8DrkC&pg=PA57
   }}</ref>
-* Space exploration
+* Space exploration<ref>{{cite journal
-* [[Cure monitoring]] of [[Composite material|composites]] using [[optical fibers]].
+ | title=Spectroscopy from Space
-* Estimating weathered wood exposure times using near infrared spectroscopy.<ref>{{cite journal|journal=WTCE 2006 – 9th World Conference on Timber Engineering|url=http://www.fpl.fs.fed.us/documnts/pdf2006/fpl_2006_wang002.pdf|title=Using NIR Spectroscopy to Predict Weathered Wood Exposure Times|year=2006|first1=Xiping|last1=Wang|first2=James P.|last2=Wacker|access-date=2009-06-22|archive-date=2021-03-01|archive-url=https://web.archive.org/web/20210301171119/https://www.fpl.fs.fed.us/documnts/pdf2006/fpl_2006_wang002.pdf|url-status=dead}}</ref>
+ | first1=Roger N. | last1=Clark | first2=Gregg A. | last2=Swayze | first3=Robert | last3=Carlson | first4=Will | last4=Grundy | first5=Keith | last5=Noll
-* Measurement of different compounds in [[food sampling|food samples]] by absorption spectroscopy both in visible and infrared spectrum.
+ | journal=Reviews in Mineralogy and Geochemistry
+ | year=2014 | volume=78 | issue=1 | pages=399–446
+ | doi=10.2138/rmg.2014.78.10 }}</ref>
+* [[Cure monitoring]] of [[Composite material|composites]] using [[optical fibers]].<ref>{{cite conference
+ | title=Composite Cure Monitoring With Infrared Transmitting Optical Fibers
+ | first1=Mark A. | last1=Druy | first2=Lucy | last2=Elandjian | first3=W. A. | last3=Stevenson
+ | series=SPIE Conference Proceedings | volume=0986
+ | conference=Fiber Optic Smart Structures and Skins, O-E/Fiber LASE '88, Boston, MA, United States
+ | publisher=Society of Photo-Optical Instrumentation Engineers
+ | date=September 6, 1988 | editor-first=Eric | editor-last=Udd
+ | doi=10.1117/12.948895 }}</ref>
+* Estimating weathered wood exposure times using near infrared spectroscopy<ref>{{cite journal | journal=WTCE 2006 – 9th World Conference on Timber Engineering | url=http://www.fpl.fs.fed.us/documnts/pdf2006/fpl_2006_wang002.pdf | title=Using NIR Spectroscopy to Predict Weathered Wood Exposure Times | year=2006 | first1=Xiping | last1=Wang | first2=James P. | last2=Wacker | access-date=2009-06-22 | archive-date=2021-03-01 | archive-url=https://web.archive.org/web/20210301171119/https://www.fpl.fs.fed.us/documnts/pdf2006/fpl_2006_wang002.pdf }}</ref>
+* Measurement of different compounds in [[food sampling|food samples]] by absorption spectroscopy both in visible and infrared spectrum<ref>{{cite journal
+ | title=Near Infrared Spectroscopy in Natural Products Analysis
+ | first=Daniel | last=Cozzolino
+ | journal=Planta Medica
+ | date=June 2009 | volume=75 | issue=7 | pages=746–756
+ | doi=10.1055/s-0028-1112220 }}</ref>
 * Measurement of toxic compounds in blood samples
-* Non-destructive elemental analysis by [[X-ray fluorescence]].
+* Non-destructive elemental analysis by [[X-ray fluorescence]]
-* Electronic structure research with various spectroscopes.
+* Electronic structure research with various spectroscopes
 * [[Redshift]] to determine the [[speed]] and [[velocity]] of a distant object
 * Determining the metabolic structure of a muscle
@@ Line 159: / Line 186: @@
 * Characterization of proteins
 * Respiratory gas analysis in hospitals<ref name="auto"/>
-* Finding the physical properties of a distant star or nearby exoplanet using the [[Relativistic Doppler effect]].<ref>{{Cite journal|bibcode = 1968JRASC..62..105S|title = The Relativistic Doppler Effect|last1 = Sher|first1 = D.|journal = Journal of the Royal Astronomical Society of Canada|year = 1968|volume = 62|page = 105}}</ref>
+* Finding the physical properties of a distant star or nearby exoplanet using the [[Relativistic Doppler effect]].<ref>{{Cite journal | bibcode=1968JRASC..62..105S | title=The Relativistic Doppler Effect | last1=Sher | first1=D. | journal=Journal of the Royal Astronomical Society of Canada | year=1968 | volume=62 | page=105 }}</ref>
-* [[In-ovo sexing]]: spectroscopy allows to determine the sex of the egg while it is hatching. Developed by French and German companies, both countries decided to ban [[chick culling]], mostly done through a macerator, in 2022.<ref>{{Cite web|url=https://www.newsendip.com/germany-and-france-will-stop-chick-culling/|title=Germany and France Will Stop Chick Culling|date=22 July 2021}}</ref>
+* [[In-ovo sexing]]: spectroscopy allows to determine the sex of the egg while it is hatching. Developed by French and German companies, both countries decided to ban [[chick culling]], mostly done through a macerator, in 2022.<ref>{{Cite web | first=Clément | last=Vérité  | title=Germany and France Will Stop Chick Culling | date=22 July 2021 | website=Newsendip| url=https://www.newsendip.com/germany-and-france-will-stop-chick-culling/ | access-date=2025-11-24 }}</ref>
 * Process monitoring  in [[Industrial process control]]<ref name="grauluque2021">{{cite journal |last1=Grau-Luque |first1=Enric |last2=Guc |first2=Maxim |last3=Becerril-Romero |first3=Ignacio |last4=Izquierdo-Roca |first4=Víctor |last5=Pérez-Rodríguez |first5=Alejandro |last6=Bolt |first6=Pieter |last7=Van den Bruele |first7=Fieke |last8=Ruhle |first8=Ulfert |title=Thickness evaluation of AlO x barrier layers for encapsulation of flexible PV modules in industrial environments by normal reflectance and machine learning |journal=Progress in Photovoltaics: Research and Applications |date=March 2022 |volume=30 |issue=3 |pages=229–239 |doi=10.1002/pip.3478 |url=https://onlinelibrary.wiley.com/doi/abs/10.1002/pip.3478 |language=en |issn=1062-7995|url-access=subscription }}</ref>
@@ Line 166: / Line 193: @@
 {{Main|History of spectroscopy}}
-The history of spectroscopy began with [[Isaac Newton]]'s optics experiments (1666–1672). According to [[Andrew Fraknoi]] and [[David Morrison (astrophysicist)|David Morrison]], "In 1672, in the first paper that he submitted to the [[Royal Society]], Isaac Newton described an experiment in which he permitted sunlight to pass through a small hole and then through a prism. Newton found that sunlight, which looks white to us, is actually made up of a mixture of all the colors of the rainbow."<ref name="open-astro">{{cite web|author1=Andrew Fraknoi|author1-link=Andrew Fraknoi|author2=David Morrison|author2-link=David Morrison (astrophysicist)|date=October 13, 2016|title=OpenStax Astronomy|url=http://cnx.org/content/col11992/latest/}}</ref> Newton applied the word "spectrum" to describe the rainbow of colors that combine to form white light and that are revealed when the white light is passed through a prism.
+The history of spectroscopy began with [[Isaac Newton]]'s optics experiments (1666–1672). According to [[Andrew Fraknoi]] and [[David Morrison (astrophysicist)|David Morrison]], "In 1672, in the first paper that he submitted to the [[Royal Society]], Isaac Newton described an experiment in which he permitted sunlight to pass through a small hole and then through a prism. Newton found that sunlight, which looks white to us, is actually made up of a mixture of all the colors of the rainbow."<ref name="open-astro">{{cite web | first1=Andrew | last1=Fraknoi | author1-link=Andrew Fraknoi | first2=David | last2=Morrison | author2-link=David Morrison (astrophysicist) | date=October 13, 2016 | title=Astronomy | website=OpenStax | url=http://cnx.org/content/col11992/latest/ | access-date=2025-11-24 }}</ref> Newton applied the word "spectrum" to describe the rainbow of colors that combine to form white light and that are revealed when the white light is passed through a prism.
-Fraknoi and Morrison state that "In 1802, [[William Hyde Wollaston]] built an improved spectrometer that included a lens to focus the Sun's spectrum on a screen. Upon use, Wollaston realized that the colors were not spread uniformly, but instead had missing patches of colors, which appeared as dark bands in the spectrum."<ref name="open-astro" /> During the early 1800s, [[Joseph von Fraunhofer]] made experimental advances with dispersive spectrometers that enabled spectroscopy to become a more precise and quantitative scientific technique. Since then, spectroscopy has played and continues to play a significant role in chemistry, physics, and astronomy. Per Fraknoi and Morrison, "Later, in 1815, German physicist Joseph Fraunhofer also examined the solar spectrum, and found about 600 such dark lines (missing colors), are now known as Fraunhofer lines, or Absorption lines."<ref name="open-astro" />{{Better source needed|date=November 2020}}
-In quantum mechanical systems, the analogous resonance is a coupling of two quantum mechanical [[stationary state]]s of one system, such as an [[atom]], via an oscillatory source of energy such as a [[photon]]. The coupling of the two states is strongest when the energy of the source matches the energy difference between the two states. The energy {{mvar|E}} of a photon is related to its frequency {{mvar|ν}} by {{math|''E'' {{=}} ''hν''}} where {{mvar|h}} is the [[Planck constant]], and so a spectrum of the system response vs. photon frequency will peak at the resonant frequency or energy. Particles such as [[electron]]s and [[neutron]]s have a comparable relationship, the [[de Broglie relations]], between their kinetic energy and their wavelength and frequency and therefore can also excite resonant interactions.
+Fraknoi and Morrison state that "In 1802, [[William Hyde Wollaston]] built an improved spectrometer that included a lens to focus the Sun's spectrum on a screen. Upon use, Wollaston realized that the colors were not spread uniformly, but instead had missing patches of colors, which appeared as dark bands in the spectrum."<ref name="open-astro" /> During the early 1800s, [[Joseph von Fraunhofer]] made experimental advances with dispersive spectrometers that enabled spectroscopy to become a more precise and quantitative scientific technique. Since then, spectroscopy has played and continues to play a significant role in chemistry, physics, and astronomy. Per Fraknoi and Morrison, "Later, in 1815, German physicist Joseph Fraunhofer examined the solar spectrum, and found about 600 such dark lines (missing colors), are now known as Fraunhofer lines, or Absorption lines."<ref name="open-astro" />{{Better source needed|date=November 2020}}
-Spectra of atoms and molecules often consist of a series of spectral lines, each one representing a resonance between two different quantum states. The explanation of these series, and the spectral patterns associated with them, were one of the experimental enigmas that drove the development and acceptance of quantum mechanics. The [[hydrogen spectral series]] in particular was first successfully explained by the [[Bohr model|Rutherford–Bohr quantum model]] of the hydrogen atom. In some cases spectral lines are well separated and distinguishable, but spectral lines can also overlap and appear to be a single transition if the [[density of states|density of energy states]] is high enough. Named series of lines include the [[principal series (spectroscopy)|principal]], [[sharp series|sharp]], [[diffuse series|diffuse]] and [[fundamental series]].
+Spectra of atoms and molecules often consist of a series of spectral lines, each one representing a resonance between two different quantum states. The explanation of these series, and the spectral patterns associated with them, were one of the experimental enigmas that drove the development and acceptance of quantum mechanics. The [[hydrogen spectral series]] in particular was first successfully explained by the [[Bohr model|Rutherford–Bohr quantum model]] of the hydrogen atom. In some cases spectral lines are well separated and distinguishable, but spectral lines can overlap and appear to be a single transition if the [[density of states|density of energy states]] is high enough. Named series of lines include the [[principal series (spectroscopy)|principal]], [[sharp series|sharp]], [[diffuse series|diffuse]] and [[fundamental series]].
-== DIY Spectroscopy ==
+== Hobbyist ==
-Spectroscopy has emerged as a growing practice within the [[Maker culture|maker movement]], enabling hobbyists and educators to construct functional spectrometers using readily available materials.<ref>{{Cite web |title=DIY Webcam Diffraction Grating Spectrometer |url=https://physicsopenlab.org/2015/11/26/webcam-diffraction-grating-spectrometer/ |access-date=2025-03-04 |website=PhysicsOpenLab |language=en-US}}</ref> Utilizing components like CD/DVD diffraction gratings, smartphones, and 3D-printed parts, these instruments offer a hands-on approach to understanding light and matter interactions. Smartphone applications<ref>{{Cite web |date=2025-02-27 |title=Spectroscope |url=https://apps.apple.com/us/app/spectroscope/id6741684078 |access-date=2025-03-04 |website=App Store |language=en-US}}</ref><ref>{{Cite web |title=Spectroscope - Apps on Google Play |url=https://play.google.com/store/apps/details?id=spectroscope.spectroscope |access-date=2025-03-04 |website=play.google.com |language=en-US}}</ref> along with open-source tools<ref>{{Citation |last=Wright |first=Les |title=leswright1977/PySpectrometer2 |date=2025-02-16 |url=https://github.com/leswright1977/PySpectrometer2 |access-date=2025-03-04}}</ref> facilitate integration, greatly simplify the capturing and analysis of spectral data. While limitations in resolution, calibration accuracy, and stray light management exist compared to professional equipment, DIY spectroscopy provides valuable educational experiences<ref>{{Cite web |title=Project Spectra! |url=https://lasp.colorado.edu/information/k-12-educators/project-spectra/ |access-date=2025-03-04 |website=Laboratory for Atmospheric and Space Physics |language=en-US}}</ref> and contributes to citizen science initiatives, fostering accessibility to spectroscopic techniques.
+Spectroscopy has emerged as a growing practice within the [[Maker culture|maker movement]], enabling hobbyists and educators to construct functional spectrometers using readily available materials.<ref>{{Cite web |title=DIY Webcam Diffraction Grating Spectrometer |url=https://physicsopenlab.org/2015/11/26/webcam-diffraction-grating-spectrometer/ |access-date=2025-03-04 |website=PhysicsOpenLab |language=en-US}}</ref> Utilizing components like CD/DVD diffraction gratings, smartphones, and 3D-printed parts, these instruments offer a hands-on approach to understanding light and matter interactions. Smartphone applications<ref>{{Cite web |date=27 February 2025 |title=Spectroscope |url=https://apps.apple.com/us/app/spectroscope/id6741684078 |access-date=2025-03-04 |website=App Store |language=en-US}}</ref><ref>{{Cite web |title=Spectroscope - Apps on Google Play |url=https://play.google.com/store/apps/details?id=spectroscope.spectroscope |access-date=2025-03-04 |website=play.google.com |language=en-US}}</ref> along with open-source tools<ref>{{Cite web |last=Wright |first=Les |title=leswright1977/PySpectrometer2 |website=[[GitHub]] |date=16 February 2025 |url=https://github.com/leswright1977/PySpectrometer2 |access-date=2025-03-04}}</ref> facilitate integration, greatly simplify the capturing and analysis of spectral data. While limitations in resolution, calibration accuracy, and stray light management exist compared to professional equipment, DIY spectroscopy provides valuable educational experiences<ref>{{Cite web |title=Project Spectra! |url=https://lasp.colorado.edu/information/k-12-educators/project-spectra/ |access-date=2025-03-04 |website=Laboratory for Atmospheric and Space Physics |language=en-US}}</ref> and contributes to citizen science initiatives, fostering accessibility to spectroscopic techniques.
 == See also ==
@@ Line 190: / Line 215: @@
 * [[Operando spectroscopy]]
 * [[Scattering theory]]
+* [[Slope spectroscopy]]
 * [[Spectral line ratios]]
 * [[Spectral power distribution]]
@@ Line 198: / Line 224: @@
 }}
-== Notes ==
+== References ==
 {{reflist|30em}}
-== References ==
+== Further reading ==
 * {{cite book|doi=10.1002/0470027320|title=Handbook of Vibrational Spectroscopy|year=2006|isbn=978-0-471-98847-2|editor1=John M. Chalmers|editor2= Peter Griffiths|publisher=Wiley|location= New York}}
 * {{cite book|url=https://books.google.com/books?id=OzAnX25h4soC&pg=PR4 |title=Applied Spectroscopy|isbn=978-0-08-052749-9|editor1=Jerry Workman|date=1998|editor2=Art Springsteen|publisher=Academic Press|location =Boston}}
@@ Line 237: / Line 263: @@
 [[Category:Spectroscopy| ]]
-[[Category:Observational astronomy]]
 [[Category:Scattering, absorption and radiative transfer (optics)]]
 [[Category:Scientific techniques]]
+[[Category:Observational astronomy]]
 [[Category:Concepts in astronomy]]
 [[Category:Gustav Kirchhoff]]

Spectroscopy: Difference between revisions

Latest revision as of 13:55, 31 December 2025

Introduction

Theory

Classification of methods

Type of radiative energy

Nature of the interaction

Type of material

Atoms

Molecules

Crystals and extended materials

Nuclei

Other types

Applications

History

Hobbyist

See also

References

Further reading

External links

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