Shell Model and Collective Excitations in ⁷²Ge

Abstract

The importance of core excitations in the shell model structure of 72Ge is investigated in a model which couples two neutrons in the p1/2 and g9/2 subshells to the low-lying excitations of 70Ge. Particle excitations from the p3/2 and f5/2 subshells are taken into account through second-order perturbation diagrams. Satisfactory agreement is obtained for energy levels and E2 and E0 rates in 72Ge in a calculation involving essentially two parameters.

Quasiparticle-phonon model calculations on doubly even Zn and Ge nuclei

“…Though in two cases for Ge, no unique assignments could be made, and the experimental data are quoted with large errors, our values are probably calculated too small. For other calculations, we refer to [35,[37][38][39]50]. …”

Structure of excited states in Se-isotopes

“…In the case of 72Ge, however, this explanation is not consistent with the observed B(E2: 0+'+2~ -) value, which strongly suggests that these two states are still members of a collective family in spite of their notable deviations in energy from the simple phonon model. In order to overcome the defect of the * Permanent address: Institute for Nuclear Study, University of Tokyo, Tanashi 188, Tokyo, Japan restricted shell-model calculation, Castel et al [5] have taken into account the collective excitations of the 7~ and obtained a good agreement with experiment. The success of this semi-microscopic model seems to suggest an important effect of interplay between the pairing and the quadrupole correlations*.…”