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1

Isomeric states and spin polarization in A approx. 90 nuclei  

Energy Technology Data Exchange (ETDEWEB)

The observed inhibition of M4 transitions in A approx. 90 nuclei has represented a long standing theoretical problem. In particular by calculating first- and second-order configuration mixing contributions to the inhibited M4 lifetimes of /sup 89/Y and /sup 87/Sr, it is found that the first-order perturbative treatment of the residual interaction usually used in shell-model calculations is unjustified in this case. Using random-phase approximation techniques, the renormalization effects of collective (''giant'') M4 resonances in /sup 88/Sr on the low energy M4 transitions in /sup 89/Y and /sup 87/Sr are investigated. It is concluded that the observed retardation of M4 lifetimes in these nuclei is consistent with the manifestation of nuclear spin polarization.

1980-04-01

2

Shell-model predictions for electromagnetic properties of N = 50 nuclei  

Energy Technology Data Exchange (ETDEWEB)

Predictions for E2, M1, and M4 transition rates and moments, together with examples of transition-charge densities, are presented for states of N = 50 nuclei. These predictions are based on one-body spectroscopic amplitudes obtained from the wave functions of a new N = 50 shell-model calculation which incorporates the 0f/sub 5/2/, 1p/sub 3/2/, 1p/sub 1/2/, and 0g/sub 9/2/ single-particle orbits and an empirically determined effective Hamiltonian for this space. The predictions are compared with experimental data, first in order to evaluate how well the model space, as applied by this Hamiltonian, accounts for observations, and then to assess the importance of configurations excluded from the model space and to determine the values of the operator renormalizations (effective charges and effective g factors) which optimally map the theoretical results onto the corresponding experimental values.

1988-12-01