Production of neutron-rich isotopes Rf264,266,268,269 by multinucleon transfer reactions based on U238 beam

Abstract

The production of neutron-rich Rf isotopes in multinucleon transfer reactions is investigated using the dinuclear system model with gemini$++$ code. The reaction $^{238}\mathrm{U}+^{252}\mathrm{Cf}$ is more advantageous to generate neutron-rich Rf isotopes than $^{238}\mathrm{U}+^{249}\mathrm{Bk}$ and $^{238}\mathrm{U}+^{248}\mathrm{Cf}$, because $^{252}\mathrm{Cf}$ has a larger $N/Z$ ratio and neutron number. The influence of incident angular momentum on the production cross sections in the $^{238}\mathrm{U}+^{252}\mathrm{Cf}$ reaction is investigated. The cross sections of primary products become larger with increasing incident energy, while the final yields of the unknown isotopes at $1.1{V}_{\text{C}}$ are slightly larger than at $1.05{V}_{\text{C}}$ and $1.2{V}_{\text{C}}$. Hence, $1.10{V}_{\text{C}}$ is a suitable incident energy in the $^{238}\mathrm{U}+^{252}\mathrm{Cf}$ reaction to produce Rf isotopes. Four unknown Rf isotopes, $^{264}\mathrm{Rf}$, $^{266}\mathrm{Rf}$, $^{268}\mathrm{Rf}$, and $^{269}\mathrm{Rf}$, are synthesized in the $^{238}\mathrm{U}+^{252}\mathrm{Cf}$ reaction with cross sections 97.2, 31.1, 0.61, and 0.04 nb, respectively. Considering the beam intensity and thickness of the target, the counts per day of those four unknown isotopes are 2724, 872, 17, and 1, respectively.