Shell-model calculations of Gamow-Teller strength in 51V, 54Fe, and 59Co.

Abstract

The Gamow-Teller (GT) strength functions of $^{51}\mathrm{V}$, $^{54}\mathrm{Fe}$, and $^{59}\mathrm{Co}$ measured by recent charge-exchange experiments have been studied using shell-model calculations employing two model spaces. The shell model is fairly successful at reproducing GT strength in the (p,n) direction, but the agreement is not as good in the (n,p) direction. It is found that both directions can be fit consistently by shifting single particle energies in a systematic manner. It is found that roughly 75% of the sum-rule strength can be seen in the experiments for both $^{51}\mathrm{V}$ and $^{54}\mathrm{Fe}$. It is also found that roughly 35% of the GT strength predicted by the shell model is seen in the (n,p) direction for all three nuclei, but that the quenching in the (p,n) direction varies with nucleus. The consequences of these findings for improving the calculation of weak interaction rates are discussed.