Fission decay properties of ultra neutron-rich uranium isotopes |
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Authors: | L Satpathy S K Patra R K Choudhury |
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Institution: | (1) Institute of Physics, Bhubaneswar, 751 005, India;(2) Nuclear Physics Division, Bhabha Atomic Research Centre, Mumbai, 400 085, India |
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Abstract: | The fission decay of highly neutron-rich uranium isotopes is investigated which shows interesting new features in the barrier
properties and neutron emission characteristics in the fission process. 233U and 235U are the nuclei in the actinide region in the beta stability valley which are thermally fissile and have been mainly used
in reactors for power generation. The possibility of occurrence of thermally fissile members in the chain of neutron-rich
uranium isotopes is examined here. The neutron number N = 162 or 164 has been predicted to be magic in numerous theoretical studies carried out over the years. The series of uranium
isotopes around it with N = 154–172 are identified to be thermally fissile on the basis of the fission barrier and neutron separation energy systematics;
a manifestation of the close shell nature of N = 162 (or 164). We consider here the thermal neutron fission of a typical representative 249U nucleus in the highly neutron-rich region. Semiempirical study of fission barrier height and width shows that 250U nucleus is stable against spontaneous fission due to increase in barrier width arising out of excess neutrons. On the basis
of the calculation of the probability of fragment mass yields and the microscopic study in relativistic mean field theory,
this nucleus is shown to undergo exotic decay mode of thermal neutron fission (multi-fragmentation fission) whereby a number
of prompt scission neutrons are expected to be simultaneously released along with the two heavy fission fragments. Such properties
will have important implications in stellar evolution involving r-process nucleosynthesis.
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Keywords: | Fission decay multi-fragmentation fission mass models relativistic mean field formalism |
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