Abstract
For the nucleosynthesis of heavy and superheavy nuclei fission becomes very important when the r-process runs in a very high neutron density environment. In part, fission is responsible for the formation of heavy nuclei due to the inclusion of fission products as new seed nuclei (fission cycling). More than that, beta-delayed fission, along with spontaneous fission, is responsible in the late stages of the r-process for the suppression of superheavy element yields.For beta-delayed fission probability calculations a model description of the beta-strength- functions is required. Extended theoretical predictions for astro-physical applications were provided long ago, and new predictions also for superheavy nuclei with uptodate nuclear input are needed. For the further extension of data to heavier transactinides the models of strength- functions should be modified, taking into account more complicated level schemes. In our present calculations the strength-function model is based on the quasi-particle approximation of Finite Fermi Systems Theory.The probabilities of beta-delayed fission and beta-delayed neutron emission are calculated for some transfermium neutron-rich nuclei, and the influence of beta-delayed fission upon superheavy element formation is discussed.
Highlights
In physical scenarios with long r-process duration fission plays an important role [1], [2]
Strong odd-even effect is explained by the structure of strength function and strong dependence of neutron separation energy on the number of neutrons, which in turn leads to strong variations of the energy window Sn − Bf and changes of ”pigmy”-resonances contributions into Pβdf and Pβdn
Calculations of beta-strength function Sβ(E) for neutron-rich nuclei is complicated task because high-energy charge-exchange excitations in continuum should be taken into account
Summary
In physical scenarios with long r-process duration fission plays an important role [1], [2]. In part beta-delayed fission, effects strongly on formation of heavy and superheavy elements and nuclei-cosmo-chronometers as well. During beta-decay of such neutron-rich nuclei, emission of delayed neutron occurs leading to broading path of the r-process. In transuranium region in addition to beta-delayed neutron emission the beta-delayed fission appeared, leading together with neutron-induced fission to termination of the nucleosynthesis of more heavier nuclei during the r-process and (mainly) after neutron freeze-out. All these beta-delayed processes [3, 4] influence on the formation of heavy (and superheavy) elements yields. Though the number of extended calculations of beta-delayed processes probabilities are exist up to Z=100 [2,3,4,5], the knowledge of these data important [6] for superheavy region (for nuclei with Z>100), as well as reevaluation of existed data
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