The most measured quantities in research on nuclear fission are the charge and mass fragments yields for uranium-235 and other fissile nuclides. In this sense, experimental results on charge distribution for low-energy fission of actinides present a preference to an even Z fragment, which is called odd-even effect on charge yield.[1]
The importance of these distributions is because they are the result of rearrangement of nucleons on the fission process due to the interplay between collective variables and individual particle levels; therefore they permit to understand several aspects of dynamics of fission process. The process from saddle (when nucleus begins its irreversible evolution to fragmentation) to scission point (when fragments are formed and nuclear interaction between fragments dispels), fissioning system shape changes but also promote nucleons to excited particle levels.
Because, for even Z (proton number) and even N (neutron number) nuclei, there is a gap from ground state to first excited particle state—which is reached by nucleon pair breaking—fragments with even Z is expected to have a higher probability to be produced than those with odd Z.
The preference even Z even N divisions is interpreted as the preservation of superfluidity during the descent from saddle to scission. The absence of odd-even effect means that process is rather viscous.[2]
Contrary to observed for charge distributions no odd-even effect on fragments mass number (A) is observed. This result is interpreted by the hypothesis that in fission process always there will be nucleon pair breaking, which may be proton pair or neutron pair breaking in low energy fission of uranium-234, uranium-236,[3] and plutonium-240 studied by Modesto Montoya.[4]
ReferencesEdit
^Siegert, G.; Greif, J.; Wollnik, H.; Fiedler, G.; Decker, R.; et al. (1975-04-21). "Nuclear Charge Distributions in the Isobars 92 to 100 Resulting from Thermal Neutron Fission of Uranium-235". Physical Review Letters. 34 (16): 1034–1036. Bibcode:1975PhRvL..34.1034S. doi:10.1103/physrevlett.34.1034.
^Bjørnholm, S (1974-01-01). "Superfluid versus Viscous Descent from Saddle to Scission". Physica Scripta. 10 (A): 110–114. Bibcode:1974PhyS...10S.110B. doi:10.1088/0031-8949/10/a/018. S2CID 250843387.
^Signarbieux, C.; Montoya, M.; Ribrag, M.; Mazur, C.; Guet, C.; Perrin, P.; Maurel, M. (1981). "Evidence for nucleon pair breaking even in the coldest scission configurations of 234U and 236U". Journal de Physique Lettres. 42 (19): 437–440. doi:10.1051/jphyslet:019810042019043700.
^Montoya, M. (1984). "Mass and kinetic energy distribution in cold fission of 233U, 235U and 239Pu induced by thermal neutrons". Zeitschrift für Physik A. 319 (2): 219–225. Bibcode:1984ZPhyA.319..219M. doi:10.1007/bf01415636. S2CID 121150912.
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nucleon, pair, breaking, fission, been, important, topic, nuclear, physics, decades, nucleon, pair, refers, nucleon, pairing, effects, which, strongly, influence, nuclear, properties, nuclide, most, measured, quantities, research, nuclear, fission, charge, mas. Nucleon pair breaking in fission has been an important topic in nuclear physics for decades Nucleon pair refers to nucleon pairing effects which strongly influence the nuclear properties of a nuclide The most measured quantities in research on nuclear fission are the charge and mass fragments yields for uranium 235 and other fissile nuclides In this sense experimental results on charge distribution for low energy fission of actinides present a preference to an even Z fragment which is called odd even effect on charge yield 1 The importance of these distributions is because they are the result of rearrangement of nucleons on the fission process due to the interplay between collective variables and individual particle levels therefore they permit to understand several aspects of dynamics of fission process The process from saddle when nucleus begins its irreversible evolution to fragmentation to scission point when fragments are formed and nuclear interaction between fragments dispels fissioning system shape changes but also promote nucleons to excited particle levels Because for even Z proton number and even N neutron number nuclei there is a gap from ground state to first excited particle state which is reached by nucleon pair breaking fragments with even Z is expected to have a higher probability to be produced than those with odd Z The preference even Z even N divisions is interpreted as the preservation of superfluidity during the descent from saddle to scission The absence of odd even effect means that process is rather viscous 2 Contrary to observed for charge distributions no odd even effect on fragments mass number A is observed This result is interpreted by the hypothesis that in fission process always there will be nucleon pair breaking which may be proton pair or neutron pair breaking in low energy fission of uranium 234 uranium 236 3 and plutonium 240 studied by Modesto Montoya 4 References Edit Siegert G Greif J Wollnik H Fiedler G Decker R et al 1975 04 21 Nuclear Charge Distributions in the Isobars 92 to 100 Resulting from Thermal Neutron Fission of Uranium 235 Physical Review Letters 34 16 1034 1036 Bibcode 1975PhRvL 34 1034S doi 10 1103 physrevlett 34 1034 Bjornholm S 1974 01 01 Superfluid versus Viscous Descent from Saddle to Scission Physica Scripta 10 A 110 114 Bibcode 1974PhyS 10S 110B doi 10 1088 0031 8949 10 a 018 S2CID 250843387 Signarbieux C Montoya M Ribrag M Mazur C Guet C Perrin P Maurel M 1981 Evidence for nucleon pair breaking even in the coldest scission configurations of 234U and 236U Journal de Physique Lettres 42 19 437 440 doi 10 1051 jphyslet 019810042019043700 Montoya M 1984 Mass and kinetic energy distribution in cold fission of 233U 235U and 239Pu induced by thermal neutrons Zeitschrift fur Physik A 319 2 219 225 Bibcode 1984ZPhyA 319 219M doi 10 1007 bf01415636 S2CID 121150912 nbsp This radioactivity related article is a stub You can help Wikipedia by expanding it vte Retrieved from https en wikipedia org w index php title Nucleon pair breaking in fission amp oldid 1165800222, wikipedia, wiki, book, books, library,
