Theoretical estimates for the synthesis of $Z=119$ superheavy nuclei with Ca, Ti, V, and Cr projectiles: effects of reaction $Q$ values and mass-model dependence

Abstract

Fusion reactions with 48Ca beams, which have been used for synthesis of $Z \le 118$ nuclei, face practical limitations for the synthesis of nuclei with $Z \ge 119$ because of the limited availability of suitable target nuclei. We estimate evaporation-residue (ER) cross sections for the reactions 48Ca + 254Es, 50Ti + 249Bk, 51V + 248Cm, and 54Cr + 243Am and examine the role of nuclear-mass-model uncertainties. We employ a hybrid framework for the three stages of the fusion reaction. The capture stage is described by the coupled-channels method, the formation stage by a Langevin approach, and the de-excitation stage by a statistical model. Using the nuclear properties from the FRDM2012 mass model, the maximum values of ER cross section summed over all xn channels are calculated to be 233, 206, 33, and 38 fb for the 48Ca + 254Es, 50Ti + 249Bk, 51V + 248Cm, and 54Cr + 243Am reactions, respectively. The relationship between the reaction Q value and the Coulomb-barrier height is found to be a key factor in comparing reactions leading to the same atomic number. In particular, the relatively small Q value magnitude of the 51V + 248Cm reaction leads to a higher excitation energy and a reduced survival probability, giving the smallest ER cross section among the reactions considered. We also find a significant mass-model dependence on the survival probability. Using the nuclear properties predicted by several mass tables yields differences in the survival probability ranging from about one to several orders of magnitude. This difference mainly originates from the neutron binding energy and shell-correction energy predicted by the nuclear mass models. The ER cross sections for the synthesis of Z = 119 nuclei are governed by both the relative relationship between the reaction Q value and the Coulomb-barrier height and nuclear-mass-model uncertainties that strongly affect the survival probability.