Nuclear Structure Studies in the 82-Neutron Region with Stripping Reactions

Abstract

The energies of the single-particle states in the $82<N<~126$ shell are determined by ($d, p$) reactions on the 82-neutron isotones ${\mathrm{Ce}}^{140}$ and ${\mathrm{Ba}}^{138}$. The results are: $f_{\frac{7}{2}}-0\mathrm{}$: $p_{\frac{3}{2}}-0.83\mathrm{}$ MeV; $f_{\frac{5}{2}}-1.88\mathrm{}$ MeV; $h_{\frac{9}{2}}-1.9\mathrm{}$ MeV; $p_{\frac{1}{2}}-2.25\mathrm{}$ MeV. The energies of the single-hole states in the 50<N ⩽ 82 shell are determined by ($d, t$) reactions on these nuclei. The results are $d_{\frac{3}{2}}-0\mathrm{}$; $s_{\frac{1}{2}}-0.27\mathrm{}$ MeV; $h_{\frac{11}{2}}-0.71\mathrm{}$ MeV; $g_{\frac{7}{2}}-1.37\mathrm{}$ MeV; $d_{\frac{5}{2}}-\simeq 2.3$ MeV. There is good agreement between determinations from the two nuclei, and the slight differences are averaged in the above results. The level structure of the 81 and 83 neutron isotopes of ${}_{61}{}^{}{}_{}{}^{}\mathrm{Pr}$ are similar to those of Ba and Ce; the splitting due to different couplings with the odd proton are small, and there is little evidence for mixing among the low-lying states. New levels are located in various isotopes of Ba, Ce, Pr, and Nd. The $d_{\frac{3}{2}}-s_{\frac{1}{2}}$ splitting in 81-neutron nuclei is measured and discussed. Information is obtained on the shell-model wave functions for the ground states of the two-hole nucleus ${\mathrm{Ba}}^{136}$ and the two-particle nuclei ${\mathrm{Ce}}^{142}$ and ${\mathrm{Nd}}^{144}$.