Quadrupole and octupole softness in the N=Z nucleus 64Ge

Quadrupole and octupole softness in the even-even N=Z nucleus 64Ge is studied on the spherical shell model basis. We carry out the shell model calculation using the pairing plus quadrupole (QQ) plus octupole (OO) interaction with monopole corrections. It is shown that 64Ge is an unstable nucleus with respect to both the quadrupole and octupole deformations, which is consistent with the previous discussions predicting the gamma softness and octupole instability. It is demonstrated that proton-neutron part QpQn of the QQ interaction is important for the gamma softness or triaxiality.