Fusion probability and survivability in estimates of heaviest nuclei production

Abstract

Abstract. Production of the heavy and heaviest nuclei (from Po to the region of superheavy elements close to Z=114 and N=184) in fusion-evaporation reactions induced by heavy ions has been considered in a systematic way within the framework of the barrier-passing model coupled with the statistical model (SM) of de-excitation of a compound nucleus (CN). Excitation functions for fission and evaporation residues (ER) measured in very asymmetric combinations can be described rather well. One can scale and fix macroscopic (liquid-drop) fission barriers for nuclei involved in the calculation of survivability with SM. In less asymmetric combinations, effects of fusion suppression caused by quasi-fission (QF) are starting to appear in the entrance channel of reactions. QF effects could be semi-empirically taken into account using fusion probabilities deduced as the ratio of measured ER cross sections to the ones obtained in the assumption of absence of the fusion suppression in corresponding reactions. SM parameters (fission barriers) obtained at the analysis of a very asymmetric combination leading to the production of (nearly) the same CN should be used for this evaluation.

Neutron-deficient superheavy nuclei obtained in the Pu240+Ca48 reaction

“…[27]. Within these three approaches, a satisfactory agreement was achieved in predicting and/or reproducing the ( 48 Ca,xn) excitation functions measured in the reactions with actinide target nuclei [29][30][31].…”

Estimates of fission barrier heights for neutron-deficient Po to Ra nuclei produced in fusion reactions

“…The possibility of quasi-fission (QF) effects [15] leading to the fusion probability P fus < 1 is not excluded in these reactions. Thus the comparison of the ER production cross sections obtained in the 16 [16,17] shows directly that P fus < 1 for the latter. These P fus values differ noticeably from those derived with the fission study [18] and obtained in the theoretical calculations [19] (Fig.…”

“…Upper panels: the ground-state shell corrections W gs in the vicinity of spherical nuclei corresponding to |β 2 | < 0.15 [13]. The fusion probabilities P fus extracted from the fission data obtained in the 48 Ca+ 154 Sm reaction [18] and similar values derived with the comparison of the ER cross sections measured in the same reaction and those obtained in 16 O+ 186 W [16,17] (symbols). P fus calculated in the framework of the DNS concept [19] is also shown for comparison by solid line.…”