Comparison ofHe3-,He4-, andC12-induced nuclear reactions in heavy-mass targets at medium excitation energies. II. Reaction model calculations

Abstract

The excitation functions for neutron emission following fusion of $^{3}\mathrm{He}$, $^{4}\mathrm{He}$, and $^{12}\mathrm{C}$ ions with a variety of heavy target nuclei, as determined in the previous communication, are compared to the statistical, exciton, and hybrid reaction model predictions. An initial exciton number of 5 is determined for $\ensuremath{\alpha}$-particle-induced reactions by the simple exciton model. The initial exciton number of 7 is consistent with the $^{3}\mathrm{He}$-induced reactions by the exciton model. The hybrid-model predictions are found to be consistent with the $^{3}\mathrm{He}$- and $^{4}\mathrm{He}$-induced reactions using the initial exciton numbers of 3 and 4, respectively. The initial pre-equilibrium exciton states are assumed to be $2p\ensuremath{-}1n$ and $2p\ensuremath{-}2n$ pure particle states, respectively. The models permitting pre-equilibrium particle emission are not consistent with the data on $^{12}\mathrm{C}$-induced reactions; however, a statistical model calculation with level density parameter $a=\frac{A}{20}$ yields reasonable agreement with the cross sections. Angular momentum effects are discussed in terms of the model predictions and the isomer ratio for helion population of $^{186}\mathrm{Ir}^{g}$ and $^{186}\mathrm{Ir}^{m}$ are determined.[NUCLEAR REACTIONS $^{197}\mathrm{Au}(^{12}\mathrm{C},xn)$, $^{209}\mathrm{Bi}(^{3}\mathrm{He},xn)$, $^{209}\mathrm{Bi}(\ensuremath{\alpha},xn)$, $^{187}\mathrm{Re}(^{3}\mathrm{He},xn)$, $^{187}\mathrm{Re}(\ensuremath{\alpha},xn)$, $^{197}\mathrm{Au}(^{3}\mathrm{He},xn)$ statistical model, exciton model, hybrid model, optical model, angular momentum; predict $\ensuremath{\sigma}(E)$ for ($\mathrm{xn}$) reactions.]