Microscopic structure of the Gamow-Teller resonance inCu58

Abstract

The Gamow-Teller (GT) states in $^{58}\mathrm{Cu}$ have been studied via the $^{58}\mathrm{Ni}(^{3}\mathrm{He},t+p)$ and $^{58}\mathrm{Ni}(^{3}\mathrm{He},t+\ensuremath{\gamma})$ coincidence experiments. The GT states in $^{58}\mathrm{Cu}$ at ${E}_{x}=6--12\phantom{\rule{0.3em}{0ex}}\text{MeV}$, where both $T=1$ and $T=2,{1}^{+}$ states exist, are excited strongly in the $^{58}\mathrm{Ni}(^{3}\mathrm{He},t)$ reaction at $E(^{3}\mathrm{He})=450\phantom{\rule{0.3em}{0ex}}\text{MeV}$ and $\ensuremath{\theta}=0\ifmmode^\circ\else\textdegree\fi{}$. Proton emissions from the GT states in $^{58}\mathrm{Cu}$ to the hole states in $^{57}\mathrm{Ni}$ have been observed with solid-state detectors in coincidence with high energy tritons measured with a magnetic spectrometer. For the first time, the $\ensuremath{\gamma}$-ray emissions from the excited states in $^{58}\mathrm{Cu}$ and in $^{57}\mathrm{Ni}$, following the $^{58}\mathrm{Ni}(^{3}\mathrm{He},t+p)$ reaction at intermediate energies, have also been observed in coincidence with tritons. Strengths of proton decay into several neutron-hole states in $^{57}\mathrm{Ni}$ and $\ensuremath{\gamma}$-decay strengths are used to discuss the wave functions of the GT states in $^{58}\mathrm{Cu}$. The $T=1$ and $T=2$ GT states do only weakly decay into a $T=3∕2,{f}_{7∕2}^{\ensuremath{-}1}$ neutron-hole state at $5.230\phantom{\rule{0.3em}{0ex}}\text{MeV}$ in $^{57}\mathrm{Ni}$, which is strongly excited via the $^{58}\mathrm{Ni}(p,d)^{57}\mathrm{Ni}$ reaction. The wave functions of the $T=1$ and $T=2$ GT states with the ${f}_{7∕2}^{\ensuremath{-}1}$ neutron-hole configuration are inferred to be strongly coupled to $2p\text{\ensuremath{-}}2h$ configurations, making fragmented GT strengths in $^{58}\mathrm{Cu}$.