Photodisintegration (also called phototransmutation, or a photonuclear reaction) is a nuclear process in which an atomic nucleus absorbs a high-energy gamma ray, enters an excited state, and immediately decays by emitting a subatomic particle. The incoming gamma ray effectively knocks one or more neutrons, protons, or an alpha particle out of the nucleus.[1] The reactions are called (γ,n), (γ,p), and (γ,α).
Photodisintegration is endothermic (energy absorbing) for atomic nuclei lighter than iron and sometimes exothermic (energy releasing) for atomic nuclei heavier than iron. Photodisintegration is responsible for the nucleosynthesis of at least some heavy, proton-rich elements via the p-process in supernovae.[which?] This causes the iron to further fuse into the heavier elements.[citation needed]
James Chadwick and Maurice Goldhaber used this reaction to measure the proton-neutron mass difference.[2] This experiment proves that a neutron is not a bound state of a proton and an electron,[why?][3] as had been proposed by Ernest Rutherford.
Photodisintegration of beryllium
A photon carrying 1.67 MeV or more energy can photodisintegrate an atom of beryllium-9 (100% of natural beryllium, its only stable isotope):
Antimony-124 is assembled with beryllium to make laboratory neutron sources and startup neutron sources. Antimony-124 (half-life 60.20 days) emits β− and 1.690MeV gamma rays (also 0.602MeV and 9 fainter emissions from 0.645 to 2.090 MeV), yielding stable tellurium-124. Gamma rays from antimony-124 split beryllium-9 into two alpha particles and a neutron with an average kinetic energy of 24keV, intermediate neutrons. The other products are two alpha particles.[4][5]
Other isotopes have higher thresholds for photoneutron production, as high as 18.72 MeV, for carbon-12.[6]
Hypernovae
In explosions of very large stars (250 or more solar masses), photodisintegration is a major factor in the supernova event. As the star reaches the end of its life, it reaches temperatures and pressures where photodisintegration's energy-absorbing effects temporarily reduce pressure and temperature within the star's core. This causes the core to start to collapse as energy is taken away by photodisintegration, and the collapsing core leads to the formation of a black hole. A portion of mass escapes in the form of relativistic jets, which could have "sprayed" the first metals into the universe.[7][8]
Photodisintegration in lightning
Terrestrial lightnings produce high-speed electrons that create bursts of gamma-rays as bremsstrahlung. The energy of these rays is sometimes sufficient to start photonuclear reactions resulting in emitted neutrons. One such reaction, 14 7N (γ,n)13 7N , is the only natural process other than those induced by cosmic rays in which 13 7N is produced on Earth. The unstable isotopes remaining from the reaction may subsequently emit positrons by β+ decay.[9]
Photofission
Photofission is a similar but distinct process, in which a nucleus, after absorbing a gamma ray, undergoes nuclear fission (splits into two fragments of nearly equal mass).
^Chadwick, J.; Goldhaber, M. (1934). "A nuclear 'photo-effect': disintegration of the diplon by γ rays". Nature. 134 (3381): 237–238. Bibcode:1934Natur.134..237C. doi:10.1038/134237a0.
^Livesy, D. L. (1966). Atomic and Nuclear Physics. Waltham, MA: Blaisdell. p. 347. LCCN 65017961.
^Lalovic, M.; Werle, H. (1970). "The energy distribution of antimonyberyllium photoneutrons". Journal of Nuclear Energy. 24 (3): 123–132. Bibcode:1970JNuE...24..123L. doi:10.1016/0022-3107(70)90058-4.
^Ahmed, S. N. (2007). Physics and Engineering of Radiation Detection. p. 51. Bibcode:2007perd.book.....A. ISBN978-0-12-045581-2.
^Handbook on Photonuclear Data for Applications: Cross-sections and Spectra. IAEA. 28 February 2019. from the original on 26 April 2017. Retrieved 24 April 2017.
^Fryer, C. L.; Woosley, S. E.; Heger, A. (2001). "Pair-Instability Supernovae, Gravity Waves, and Gamma-Ray Transients". The Astrophysical Journal. 550 (1): 372–382. arXiv:astro-ph/0007176. Bibcode:2001ApJ...550..372F. doi:10.1086/319719. S2CID 7368009.
^Heger, A.; Fryer, C. L.; Woosley, S. E.; Langer, N.; Hartmann, D. H. (2003). "How Massive Single Stars End Their Life". The Astrophysical Journal. 591 (1): 288–300. arXiv:astro-ph/0212469. Bibcode:2003ApJ...591..288H. doi:10.1086/375341. S2CID 59065632.
^Enoto, Teruaki; Wada, Yuuki; Furuta, Yoshihiro; Nakazawa, Kazuhiro; Yuasa, Takayuki; Okuda, Kazufumi; Makishima, Kazuo; Sato, Mitsuteru; Sato, Yousuke; Nakano, Toshio; Umemoto, Daigo (2017-11-23). "Photonuclear Reactions in Lightning Discovered from Detection of Positrons and Neutrons". Nature. 551 (7681): 481–484. arXiv:1711.08044. doi:10.1038/nature24630. PMID 29168803. S2CID 4388159. from the original on 2020-11-27. Retrieved 2020-12-19.
January 21, 2023
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This article needs additional citations for verification Please help improve this article by adding citations to reliable sources Unsourced material may be challenged and removed Find sources Photodisintegration news newspapers books scholar JSTOR March 2011 Learn how and when to remove this template message Photodisintegration also called phototransmutation or a photonuclear reaction is a nuclear process in which an atomic nucleus absorbs a high energy gamma ray enters an excited state and immediately decays by emitting a subatomic particle The incoming gamma ray effectively knocks one or more neutrons protons or an alpha particle out of the nucleus 1 The reactions are called g n g p and g a Photodisintegration is endothermic energy absorbing for atomic nuclei lighter than iron and sometimes exothermic energy releasing for atomic nuclei heavier than iron Photodisintegration is responsible for the nucleosynthesis of at least some heavy proton rich elements via the p process in supernovae which This causes the iron to further fuse into the heavier elements citation needed Contents 1 Photodisintegration of deuterium 2 Photodisintegration of beryllium 3 Hypernovae 4 Photodisintegration in lightning 5 Photofission 6 See also 7 ReferencesPhotodisintegration of deuterium EditA photon carrying 2 22 MeV or more energy can photodisintegrate an atom of deuterium 21 D g 11 H nJames Chadwick and Maurice Goldhaber used this reaction to measure the proton neutron mass difference 2 This experiment proves that a neutron is not a bound state of a proton and an electron why 3 as had been proposed by Ernest Rutherford Photodisintegration of beryllium EditA photon carrying 1 67 MeV or more energy can photodisintegrate an atom of beryllium 9 100 of natural beryllium its only stable isotope 94 Be g 2 42 He nAntimony 124 is assembled with beryllium to make laboratory neutron sources and startup neutron sources Antimony 124 half life 60 20 days emits b and 1 690MeV gamma rays also 0 602MeV and 9 fainter emissions from 0 645 to 2 090 MeV yielding stable tellurium 124 Gamma rays from antimony 124 split beryllium 9 into two alpha particles and a neutron with an average kinetic energy of 24keV intermediate neutrons The other products are two alpha particles 4 5 12451 Sb 12452 Te b gOther isotopes have higher thresholds for photoneutron production as high as 18 72 MeV for carbon 12 6 Hypernovae EditIn explosions of very large stars 250 or more solar masses photodisintegration is a major factor in the supernova event As the star reaches the end of its life it reaches temperatures and pressures where photodisintegration s energy absorbing effects temporarily reduce pressure and temperature within the star s core This causes the core to start to collapse as energy is taken away by photodisintegration and the collapsing core leads to the formation of a black hole A portion of mass escapes in the form of relativistic jets which could have sprayed the first metals into the universe 7 8 Photodisintegration in lightning EditTerrestrial lightnings produce high speed electrons that create bursts of gamma rays as bremsstrahlung The energy of these rays is sometimes sufficient to start photonuclear reactions resulting in emitted neutrons One such reaction 147 N g n 137 N is the only natural process other than those induced by cosmic rays in which 137 N is produced on Earth The unstable isotopes remaining from the reaction may subsequently emit positrons by b decay 9 Photofission EditPhotofission is a similar but distinct process in which a nucleus after absorbing a gamma ray undergoes nuclear fission splits into two fragments of nearly equal mass See also EditPair instability supernova Silicon burning processReferences Edit Clayton D D 1984 Principles of Stellar Evolution and Nucleosynthesis University of Chicago Press pp 519 ISBN 978 0 22 610953 4 Chadwick J Goldhaber M 1934 A nuclear photo effect disintegration of the diplon by g rays Nature 134 3381 237 238 Bibcode 1934Natur 134 237C doi 10 1038 134237a0 Livesy D L 1966 Atomic and Nuclear Physics Waltham MA Blaisdell p 347 LCCN 65017961 Lalovic M Werle H 1970 The energy distribution of antimonyberyllium photoneutrons Journal of Nuclear Energy 24 3 123 132 Bibcode 1970JNuE 24 123L doi 10 1016 0022 3107 70 90058 4 Ahmed S N 2007 Physics and Engineering of Radiation Detection p 51 Bibcode 2007perd book A ISBN 978 0 12 045581 2 Handbook on Photonuclear Data for Applications Cross sections and Spectra IAEA 28 February 2019 Archived from the original on 26 April 2017 Retrieved 24 April 2017 Fryer C L Woosley S E Heger A 2001 Pair Instability Supernovae Gravity Waves and Gamma Ray Transients The Astrophysical Journal 550 1 372 382 arXiv astro ph 0007176 Bibcode 2001ApJ 550 372F doi 10 1086 319719 S2CID 7368009 Heger A Fryer C L Woosley S E Langer N Hartmann D H 2003 How Massive Single Stars End Their Life The Astrophysical Journal 591 1 288 300 arXiv astro ph 0212469 Bibcode 2003ApJ 591 288H doi 10 1086 375341 S2CID 59065632 Enoto Teruaki Wada Yuuki Furuta Yoshihiro Nakazawa Kazuhiro Yuasa Takayuki Okuda Kazufumi Makishima Kazuo Sato Mitsuteru Sato Yousuke Nakano Toshio Umemoto Daigo 2017 11 23 Photonuclear Reactions in Lightning Discovered from Detection of Positrons and Neutrons Nature 551 7681 481 484 arXiv 1711 08044 doi 10 1038 nature24630 PMID 29168803 S2CID 4388159 Archived from the original on 2020 11 27 Retrieved 2020 12 19 Retrieved from https en wikipedia org w index php title Photodisintegration amp oldid 1079216251, wikipedia, wiki, book, books, library,
