(He4,t) Reaction on Medium-Weight Nuclei

Abstract

A 26.7-MeV beam of ${\mathrm{He}}^4$ ions from the Los Alamos variable-energy cyclotron was used to study the (${\mathrm{He}}^4,t$) reaction on ${\mathrm{Cr}}^{52}$, ${\mathrm{Fe}}^{54}$, ${\mathrm{Fe}}^{56}$, ${\mathrm{Fe}}^{58}$, ${\mathrm{Co}}^{59}$, ${\mathrm{Ni}}^{60}$, ${\mathrm{Ni}}^{62}$, and ${\mathrm{Ni}}^{64}$. Angular distributions of tritons from the more strongly excited states of the residual nuclei were obtained over the angular range of ${11}^{\circ }\lesssim {\theta }_{\mathrm{c}.\mathrm{m}.\mathrm{}}\lesssim {48}^{\circ }$. There are marked differences between distributions from ${\frac{3}{2}}^{-}$ states and ${\mathrm{½}}^{-}$ states, and between distributions from ${\frac{7}{2}}^{-}$ states and ${\frac{5}{2}}^{-}$ states. The behavior of the distributions also appears to depend strongly upon the $Q$ of the reaction. The experimental results are compared to the predictions of a spin-independent distorted-wave calculation. Although such a calculation cannot reproduce the $j$-dependent behavior of the distributions, the extracted spectroscopic factors are usually in acceptable agreement with those obtained from recent (${\mathrm{He}}^3,d$) reaction studies on these nuclides, and thus a meaningful comparison of the results from the (${\mathrm{He}}^4,t$) and (${\mathrm{He}}^3,d$) reaction studies can be made. This provides evidence that under the conditions of the studies, core-excitation mechanisms are relatively unimportant.