Structure of Odd-AIndium Isotopes Determined by the (d,He3) Reaction

The nuclear structure of the odd-$A$ indium isotopes with masses 115, 117, 119, 121, and 123 has been studied using the proton pickup reaction Sn ($d$, ${}_{}{}^3{}_{}{}^{}\mathrm{He}$) In with a deuteron bombarding energy of 28.9 MeV. Seven or more levels have been observed in each isotope. Excitation energies have been measured and $l$ values and spectroscopic factors have been extracted from the measured angular distributions. Ground-state $Q$ values have been measured relative to that for ${}_{}{}^{116}{}_{}{}^{}\mathrm{Sn}$. The five ($d$, ${}_{}{}^3{}_{}{}^{}\mathrm{He}$) spectra are quite similar. The ground state and levels at approximately 0.3 and 0.6 MeV in each nucleus are excited by pickup of a proton from the $1g_{\frac{9}{2}}$, $2p_{\frac{1}{2}}$, and $2p_{\frac{3}{2}}$ orbitals, respectively. These three levels contain approximately 70% of the $g_{\frac{9}{2}}$ sum-rule strength, 75% of the $p_{\frac{1}{2}}$ strength, and 50% of the $p_{\frac{3}{2}}$ strength. There is evidence for additional $g_{\frac{9}{2}}$ strength in $l=4\mathrm{}$ transitions near 1.4 MeV in each isotope. The existence of these transitions can be explained by an admixture of the $g_{\frac{9}{2}}$ hole configuration with the ${\frac{9}{2}}^{+}$ member of the multiplet formed by coupling a $g_{\frac{9}{2}}$ hole to the collective $2^{+}$ state near 1.2 MeV in the tin core. Transitions to levels weakly excited near 1.0 MeV in ${}_{}{}^{115}{}_{}{}^{}\mathrm{In}$, ${}_{}{}^{117}{}_{}{}^{}\mathrm{In}$, and ${}_{}{}^{119}{}_{}{}^{}\mathrm{In}$ are best reproduced with $l=2\mathrm{}$ distorted-wave-approximation curves. If these levels are populated by a one-step $l=2\mathrm{}$ direct reaction, it indicates a nonclosure of the $Z=50\mathrm{}$ proton shell in the tin ground state. Surprisingly, no $l=3\mathrm{}$ transitions corresponding to pickup of protons from the $1f_{\frac{5}{2}}$ orbital were observed, even though most of the isotopes were studied up to 3.5-MeV excitation.