View source for Neutronium

{{short description|Hypothetical substance in nuclear physics}}

'''Neutronium''' (or '''neutrium''',<ref name=InglisArkell>{{cite web | last = Inglis-Arkell | first = Esther | url = http://io9.com/5899961/neutrium-the-most-neutral-hypothetical-state-of-matter-ever | title = Neutrium: The Most Neutral Hypothetical State of Matter Ever | work = [[io9.com]] | date = 2012-04-14 | access-date = 2013-02-11 | archive-date = 2014-11-12 | archive-url = https://web.archive.org/web/20141112052011/http://io9.com/5899961/neutrium-the-most-neutral-hypothetical-state-of-matter-ever | url-status = live }}</ref> '''neutrite,'''<ref name="Zhuravleva">{{Cite book|url=https://books.google.com/books?id=HpttCzNiB6wC&pg=PA75|title=Ballad of the Stars: Stories of Science Fiction, Ultraimagination, and TRIZ|last=Zhuravleva|first=Valentina|date=2005|publisher=Technical Innovation Center, Inc.|isbn=978-0-9640740-6-4|page=75|access-date=2019-04-25|archive-date=2022-04-12|archive-url=https://web.archive.org/web/20220412033116/https://books.google.com/books?id=HpttCzNiB6wC&pg=PA75|url-status=live}}</ref> or '''element zero''') is a hypothetical substance made purely of [[neutron]]s. The word was coined by scientist [[Andreas von Antropoff]] in 1926 (before the 1932 [[discovery of the neutron]]) for the hypothetical "element of atomic number zero" (with no protons in its nucleus) that he placed at the head of the [[periodic table]] (denoted by -).<ref name='Antropoff 1926'>{{cite journal | last = von Antropoff | first = A. | title = Eine neue Form des periodischen Systems der Elementen | journal = [[Zeitschrift für Angewandte Chemie]] | date = 1926 | volume = 39 | issue = 23 | pages = 722–725 | doi = 10.1002/ange.19260392303| bibcode = 1926AngCh..39..722V |lang=de}}</ref><ref name='Stewart 2007'>{{cite journal | last = Stewart | first = P. J. | title = A century on from Dmitrii Mendeleev: Tables and spirals, noble gases and Nobel prizes | journal = [[Foundations of Chemistry]] | date = 2007 | volume = 9 | issue = 3 | pages = 235–245 | doi = 10.1007/s10698-007-9038-x | s2cid = 97131841 }}</ref> However, the meaning of the term has [[semantic change|changed over time]], and from the last half of the 20th century onward it has been also used to refer to extremely dense substances resembling the [[neutron-degenerate matter]] theorized to exist in the cores of [[neutron star]]s.

==In neutron stars==
{{Main|Neutron star}}
[[Image:Neutron star cross section.svg|thumb|Cross-section of neutron star. Here, the core has [[Neutron|neutrons]] or [[Neutron degenerate matter|neutron-degenerate matter]] and [[quark matter]].]]
Neutronium is used in popular physics literature<ref name=InglisArkell/><ref name=Zhuravleva/> to refer to the material present in the cores of neutron stars (stars which are too massive to be supported by [[electron degeneracy pressure]] and which collapse into a denser phase of matter). In scientific literature the term  "neutron-degenerate matter"<ref>{{cite book | last1 = Angelo | first1 = J. A. | date = 2006 | title = Encyclopedia of Space and Astronomy | url = https://books.google.com/books?id=VUWno1sOwnUC&pg=PA178 | page = 178 | publisher = [[Infobase Publishing]] | isbn = 978-0-8160-5330-8 | access-date = 2016-10-28 | archive-date = 2019-12-15 | archive-url = https://web.archive.org/web/20191215113119/https://books.google.com/books?id=VUWno1sOwnUC&pg=PA178 | url-status = live }}</ref> or simply [[neutron matter]] is used for this material.<ref>{{Cite journal |last1=Gandolfi |first1=Stefano |last2=Gezerlis |first2=Alexandros |last3=Carlson |first3=J. |date=2015-10-19 |title=Neutron Matter from Low to High Density |url=https://www.annualreviews.org/doi/10.1146/annurev-nucl-102014-021957 |journal=Annual Review of Nuclear and Particle Science |language=en |volume=65 |issue=1 |pages=303–328 |doi=10.1146/annurev-nucl-102014-021957 |issn=0163-8998|arxiv=1501.05675 |bibcode=2015ARNPS..65..303G }}</ref>

==Hypothetical multi-neutrons==
The term "neutronium" was coined in 1926 by Andreas von Antropoff for a conjectured form of matter made up of [[neutrons]] with no [[proton]]s or [[electron]]s, which he placed as the [[chemical element]] of [[atomic number]] zero at the head of his new version of the [[periodic table]].<ref name='Antropoff 1926'/> It was subsequently placed in the middle of several spiral representations of the periodic system for classifying the chemical elements, such as those of [[Charles Janet]] (1928), [[Edgar Emerson]] (1944),<ref>{{cite journal |title=A new spiral form of the periodic table |date=1944 |last1=Emerson |first1=Edgar I. |journal=Journal of Chemical Education |volume=21 |issue=3 |page=111 |bibcode=1944JChEd..21..111E |doi=10.1021/ed021p111 }}</ref><ref>{{cite journal| title=A chart based on atomic numbers showing the electronic structure of the elements| date=1944| last1=Emerson| first1=Edgar I.| journal=Journal of Chemical Education| volume=21| issue=5| page=254| bibcode=1944JChEd..21..254E| doi=10.1021/ed021p254}}</ref> and [[John Drury Clark|John D. Clark]] (1950).

{{anchor|Isotopes}}The term is not used in the scientific literature either for a condensed form of matter, or as an element, and theoretical analysis expects no bound forms of neutrons without protons.<ref>{{cite journal | last = Timofeyuk | first = N. K. | title = Do multineutrons exist? | date = 2003 | volume = 29 | issue = 2 | page = L9 | journal = [[Journal of Physics G]] | arxiv = nucl-th/0301020 | bibcode = 2003JPhG...29L...9T | doi = 10.1088/0954-3899/29/2/102 | s2cid = 2847145 }}</ref> 

===Scattering resonances with multiple neutrons===

The dineutron, containing two neutrons, is not a stable bound particle, but an extremely short-lived resonance state produced by nuclear reactions in the decay of beryllium-16. Evidence reported in 2012 for the resonance<ref>{{cite journal | author = Schirber, M. | title = Nuclei Emit Paired-up Neutrons | journal = [[Physics (American Physical Society magazine)|Physics]] | date = 2012 | volume = 5 | article-number = 30 | doi = 10.1103/Physics.5.30 | bibcode = 2012PhyOJ...5...30S }}</ref><ref>{{cite journal | author = Spyrou, A. | display-authors = 4 | author2 = Kohley, Z. | author3 = Baumann, T. | author4 = Bazin, D. | author5 = Brown, B. A. | author6 = Christian, G. | author7 = DeYoung, P. A. | author8 = Finck, J. E. | author9 = Frank, N. | author10 = Lunderberg, E. | author11 = Mosby, S. | author12 = Peters, W. A. | author13 = Schiller, A. | author14 = Smith, J. K. | author15 = Snyder, J. | author16 = Strongman, M. J. | author17 = Thoennessen, M. | author18 = Volya, A. | title = First Observation of Ground State Dineutron Decay: <sup>16</sup>Be | journal = [[Physical Review Letters]] | date = 2012 | volume = 108 | issue = 10 | article-number = 102501 | doi = 10.1103/PhysRevLett.108.102501 | pmid = 22463404 | bibcode = 2012PhRvL.108j2501S | osti = 1104191 | doi-access = free }}</ref> was disputed,<ref>Marqués, F. M., Orr, N. A., Achouri, N. L., Delaunay, F., & Gibelin, J. (2012). Comment on "First Observation of Ground State Dineutron Decay: Be 16". Physical Review Letters, 109(23), 239201.</ref> but new work reportedly clears up the issues.<ref>{{Cite journal |last1=Monteagudo |first1=B. |last2=Marqués |first2=F. M. |last3=Gibelin |first3=J. |last4=Orr |first4=N. A. |last5=Corsi |first5=A. |last6=Kubota |first6=Y. |last7=Casal |first7=J. |last8=Gómez-Camacho |first8=J. |last9=Authelet |first9=G. |last10=Baba |first10=H. |last11=Caesar |first11=C. |last12=Calvet |first12=D. |last13=Delbart |first13=A. |last14=Dozono |first14=M. |last15=Feng |first15=J. |date=2024-02-23 |title=Mass, Spectroscopy, and Two-Neutron Decay of $^{16}\mathrm{Be}$ |url=https://eprints.whiterose.ac.uk/211204/1/2401.16817.pdf |journal=Physical Review Letters |volume=132 |issue=8 |article-number=082501 |doi=10.1103/PhysRevLett.132.082501 |pmid=38457706 |osti=2473832 }}</ref>

The dineutron hypothesis had been used in theoretical studies of the structure of [[exotic nuclei]]. For example <sup>11</sup>Li is modeled as a dineutron bound to a <sup>9</sup>Li core.<ref name="Bertulani 1993 281–376">{{cite journal | last1 = Bertulani | first1 = C. A. | last2 = Canto | first2 = L. F. | last3 = Hussein | first3 = M. S. | title = The Structure And Reactions Of Neutron-Rich Nuclei | journal = [[Physics Reports]] | date = 1993 | volume = 226 | issue = 6 | pages = 281–376 | bibcode = 1993PhR...226..281B | doi = 10.1016/0370-1573(93)90128-Z | url = http://www.tamu-commerce.edu/physics/carlos/papers/PRep226_1993_281.pdf | archive-url = https://web.archive.org/web/20110928120249/http://www.tamu-commerce.edu/physics/carlos/papers/PRep226_1993_281.pdf | archive-date = 2011-09-28 }}</ref><ref>{{cite journal | last1 = Hagino | first1 = K. | last2 = Sagawa | first2 = H. | last3 = Nakamura | first3 = T. | last4 = Shimoura | first4 = S. | title = Two-particle correlations in continuum dipole transitions in Borromean nuclei | journal = [[Physical Review C]] | date = 2009 | volume = 80 | issue = 3 | page = 1301 | arxiv = 0904.4775 | bibcode = 2009PhRvC..80c1301H | doi = 10.1103/PhysRevC.80.031301 | s2cid = 119293335 }}</ref> A system made up of only two neutrons is not bound, though the attraction between them is very nearly enough to make them so.<ref>{{cite journal | last1 = MacDonald | first1 = J. | last2 = Mullan | first2 = D. J. | date = 2009 | title = Big Bang Nucleosynthesis: The Strong Nuclear Force meets the Weak Anthropic Principle | journal = [[Physical Review D]] | volume = 80 | issue = 4 | page = 3507 | arxiv = 0904.1807 | bibcode = 2009PhRvD..80d3507M | doi = 10.1103/PhysRevD.80.043507 | s2cid = 119203730 }}</ref> This has some consequences on [[nucleosynthesis]] and the [[abundance of the chemical elements]].<ref name="Bertulani 1993 281–376"/><ref>{{cite journal | last1 = Kneller | first1 = J. P. | last2 = McLaughlin | first2 = G. C. | author2-link = Gail McLaughlin | title = The Effect of Bound Dineutrons upon BBN | journal = [[Physical Review D]] | date = 2004 | volume = 70 | issue = 4 | page = 3512 | arxiv = astro-ph/0312388 | bibcode = 2004PhRvD..70d3512K | doi = 10.1103/PhysRevD.70.043512 | s2cid = 119060865 }}</ref>

A trineutron state consisting of three bound neutrons has not been detected, and is not expected to be bound.<ref>{{cite journal |title=Ab initio no-core Gamow shell-model calculations of multineutron systems |first1=J. G. |last1=Li |first2=N. |last2=Michel |first3=B. S. |last3=Hu |first4=W. |last4=Zuo |first5=F. R. |last5=Xu |journal=Physical Review C |volume=100 |issue= 5|date=2019 |article-number=054313 |doi=10.1103/PhysRevC.100.054313 |arxiv=1911.06485|bibcode=2019PhRvC.100e4313L }}</ref>

A [[tetraneutron]] is a hypothetical particle consisting of four bound neutrons. Reports of its existence have not been replicated.<ref>{{cite journal | last1 = Bertulani | first1 = C. A. | last2 = Zelevinsky | first2 = V. | year = 2003 | title = Is the tetraneutron a bound dineutron-dineutron molecule? | journal = [[Journal of Physics G]] | volume = 29 | issue = 10 | pages = 2431–2437 | arxiv = nucl-th/0212060 | bibcode = 2003JPhG...29.2431B | doi = 10.1088/0954-3899/29/10/309 | s2cid = 55535943 }}</ref><ref>[https://scitechdaily.com/tetra-neutron-experiment-understanding-of-nuclear-forces-might-have-to-be-significantly-changed/ "Tetra-Neutron Experiment: Understanding of Nuclear Forces Might Have To Be Significantly Changed"]. {{Webarchive|url=https://web.archive.org/web/20211213090609/https://scitechdaily.com/tetra-neutron-experiment-understanding-of-nuclear-forces-might-have-to-be-significantly-changed/ |date=2021-12-13 }}. SciTechDaily, December 12, 2021. Technical University of Munich (TUM)</ref>

Calculations indicate that the hypothetical pentaneutron state, consisting of a cluster of five neutrons, would not be bound.<ref>{{cite journal | last1 = Bevelacqua | first1 = J. J. | title = Particle stability of the pentaneutron | journal = [[Physics Letters B]] | date = 1981 | volume = 102 | issue = 2–3 | pages = 79–80 | bibcode = 1981PhLB..102...79B | doi = 10.1016/0370-2693(81)91033-9 }}</ref>

==See also==
* {{annotated link|Compact star}}

==References==
{{reflist|25em}}

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