Neutron Hole States inZ=40Nuclei Studied with the (p,d) Reaction onZr90,Zr91, andZr92

Abstract

The ($p,d$) reaction on ${}_{}{}^{90}{}_{}{}^{}\mathrm{Zr}$, ${}_{}{}^{91}{}_{}{}^{}\mathrm{Zr}$, and ${}_{}{}^{92}{}_{}{}^{}\mathrm{Zr}$ was studied at a proton energy of 31 MeV. Deuteron spectra were measured with a broad-range magnetic spectrograph. The reaction on ${}_{}{}^{90}{}_{}{}^{}\mathrm{Zr}$ excites strongly the ground state of ${}_{}{}^{89}{}_{}{}^{}\mathrm{Zr}$ ($l=4\mathrm{}$) and excited states at 0.588 MeV ($l=1\mathrm{}$), 1.094 MeV ($l=1\mathrm{}$), and 1.450 MeV ($l=3\mathrm{}$). These states are shown to be consistent with pickup of neutrons from the $1g_{\frac{9}{2}}$, $2p_{\frac{1}{2}}$, $2p_{\frac{3}{2}}$, and $1f_{\frac{5}{2}}$ shell-model levels, respectively. On this basis definite spin-parity assignments are made to these levels. Small portions of the strength for pickup of these neutrons are also observed for higher excited states. The reaction on ${}_{}{}^{91}{}_{}{}^{}\mathrm{Zr}$ excites the states corresponding to the creation of the $1g_{\frac{9}{2}}$ hole and the consequent coupling of this hole to a $2d_{\frac{5}{2}}$ neutron. All six of the expected one-particle one-hole states are observed. The ${}_{}{}^{92}{}_{}{}^{}\mathrm{Zr}$ target, which was included to study the effect of this isotopic impurity in the ${}_{}{}^{91}{}_{}{}^{}\mathrm{Zr}$ target, yielded data on a number of excited states in ${}_{}{}^{91}{}_{}{}^{}\mathrm{Zr}$.