We examine two recent effective shell model interactions, JUN45 and JJ4B, that have been proposed for use in the $f_{5/2},p_{3/2},p_{1/2},g_{9/2}$ model space for both protons and neutrons. We calculate a number of quantities that did not enter into the fits undertaken to fix the parameters of both interactions. In particular we consider the static quadrupole moments ($Q$’s) of excited states of the even-even ${}^{70-76}\mathrm{Ge}$ isotopes, as well as the $B(E2)$ values in these nuclei. (We previously studied ${}^{70}\mathrm{Zn}$ isotopes using JJ4B.) Some striking disagreements between the JUN45 predictions and the experimental results had already been noted for the quadrupole moments of the $2_1^{+}$ states, $Q(2_1^{+}$)’s, of these nuclei. We investigate whether these discrepancies also occur for the JJ4B interaction. Subsequently, we also apply both interactions to calculate the $Q$’s of some more highly excited states and compare the two sets of predictions regarding the nature of the nuclear states under consideration. We seek to understand the measured signs of the $Q(2_1^{+}$)’s in the isotopic Ge chain by looking at a simple single-$J$ shell model and also at the collective vibrational and rotational pictures.

• Received 14 July 2010

DOI:https://doi.org/10.1103/PhysRevC.83.027302