Neutron-hole strengths and core coupling in 87Sr via the 88Sr(3He, alpha )87Sr reaction.

Abstract

Neutron-hole states in /sup 87/Sr were studied by means of the /sup 88/Sr(/sup 3/He,..cap alpha..)/sup 87/Sr reaction at 36 MeV. Angular distribution measurements were carried out from 3/sup 0/ to 41/sup 0/ (lab) and analyzed with the zero-range distorted-wave Born approximation method. Spectroscopic factors have been determined for about 50 discrete levels in /sup 87/Sr located below 6 MeV excitation energy and for the three lowest isobaric analog states 2p(3/2, 1f(5/2, and 2p(1/2 observed around 11 MeV. Many l = 1 and l = 3 discrete levels are observed in the 3--6 MeV excitation energy range. In addition, a large part of the 1f-2p strength is found to lie in the higher-lying continuum up to 13 MeV (about 10% and 40% for the l = 1 and 3 contributions, respectively). The distribution of the 1f-2p neutron-hole strength is compared to previous data on neighboring nuclei /sup 89/Zr and /sup 91/Mo. In addition, angular distributions for some low-lying high-spin states in /sup 87/Sr are nicely reproduced by coupled-channel calculations which assume pure two-step (inelastic plus g(9/2 transfer) processes. Spin-parity assignments are proposed for the levels at 1.92 MeV ((7/2/sup +/), 2.16 MeV ((11/2/sup +/), 2.55 MeV ((9/2/sup -/), and 2.60 MeVmore » ((13/2/sup -/), on the basis of this coupled-channel analysis.« less