Production of proton-rich nuclei around Z=84-90 in fusion-evaporation reactions

TL;DR

This study systematically investigates the production cross sections of proton-rich nuclei with Z=84-90 using the dinuclear system model, analyzing optimal conditions and key nuclear effects relevant for experimental synthesis.

Contribution

It provides a comprehensive analysis of fusion-evaporation reactions for producing proton-rich nuclei around Z=84-90, including optimal energies, evaporation channels, and the influence of nuclear shell effects.

Findings

Neutron shell closure N=126 significantly affects neutron evaporation.

Charged particle evaporation, especially alpha and proton, is comparable to neutron evaporation.

Production cross section increases with mass asymmetry of colliding systems.

Abstract

Within the framework of the dinuclear system model, production cross sections of proton-rich nuclei with charged numbers of Z=84-90 are investigated systematically. Possible combinations with the $^{28}$Si, $^{32}$S, $^{40}$Ar bombarding the target nuclides $^{165}$Ho, $^{169}$Tm, $^{170-174}$Yb, $^{175,176}$Lu, $^{174,176-180}$Hf and $^{181}$Ta are analyzed thoroughly. The optimal excitation energies and evaporation channels are proposed to produce the proton-rich nuclei. The systems are feasible to be constructed in experiments. It is found that the neutron shell closure of N=126 is of importance during the evaporation of neutrons. The experimental excitation functions in the $^{40}$Ar induced reactions can be nicely reproduced. The charged particle evaporation is comparable with neutrons in cooling the excited proton-rich nuclei, in particular for the channels with $\alpha$ and proton evaporation. The production cross section increases with the mass asymmetry of colliding systems because of the decrease of the inner fusion barrier. The channels with pure neutron evaporation depend on the isotopic targets. But it is different for the channels with charged particles and more sensitive to the odd-even effect.