Fusion-evaporation residues andα-decay chains of the superheavy elementZ=115formed in the243Am+48Ca reaction using the dynamical cluster-decay model

Abstract

The decay of the $Z=115$ superheavy nuclear system, formed in the ${}^{243}\mathrm{Am}+{}^{48}\mathrm{Ca}$ reaction, is studied by using the dynamical cluster-decay model. The calculated excitation functions of $2n$-, $3n$-, and $4n$-evaporation channels, for the excitation energy range ${E}_{\mathrm{CN}}^{*}=31$--47 MeV, are compared with the recent experimental data. The deformation effects are included up to ${\ensuremath{\beta}}_{2}$, within the hot optimum orientation approach, and a comparative analysis of spherical versus static and dynamic deformations is investigated explicitly for the $2n$-evaporation residue, as only $2n$ decay responds to spherical fragments. The $3n$ and $4n$ decay cross sections could be fitted only after the inclusion of deformation effects. The variation of preformation probability, barrier penetrability, and barrier modification is investigated in order to extract a better picture of the dynamics involved in the reaction under consideration. It is observed that, for the $3n$-evaporation channel, the barrier modification at ${E}_{\mathrm{CN}}^{*}=36.15$ MeV is the smallest and hence supports the experimental observation of maximum cross section (8.5 pb) at this energy. The role of isospin ($N/Z$ ratio) is also investigated for the decay of various isotopes of $Z=115$ formed in ${}^{48}\text{Ca}\phantom{\rule{0.16em}{0ex}}+{\phantom{\rule{0.16em}{0ex}}}^{241,243,245}$Am reactions. Furthermore, the evaporation cross sections of $2n$, $3n,$ and $4n$ channels are also estimated at the Bass barrier by interpolating the neck-length parameters fixed in reference to available data at above-barrier energies. Finally, the $\ensuremath{\alpha}$-decay chains are analyzed by using the preformed cluster model. It is shown that the present data of $\ensuremath{\alpha}$-decay half-lives support ``hot'' optimum orientations of nuclei, rather than the usual ``cold'' ones, within a constant empirical factor in penetrability.