Triaxiality and the nature of low-energy excitations in Ge 76

Abstract

The deformation properties of the low-lying states in Ge76 have been investigated following a safe-energy Coulomb excitation measurement with the GRETINA tracking array and CHICO2 heavy-ion counter at the ATLAS accelerator facility at Argonne National Laboratory. A comprehensive set of transition and static E2 matrix elements were extracted from the measured differential Coulomb cross sections and compared with results of configuration-interaction shell-model calculations and computations carried out within the framework of the generalized triaxial rotor model. The remarkable agreement between the calculated and experimental data supports a near-maximum triaxial deformation for the ground state of Ge76. In addition, the degree of softness of the asymmetry in Ge76 and Se76 was investigated using rotational invariants generated from configuration-interaction shell-model wave functions computed with the jj44b and JUN45 effective interactions. The resulting invariants are shown to be consistent with a stiff triaxial deformation in Ge76 and a predominantly soft triaxial potential for Se76, in agreement with the conclusions of recent works by this collaboration.