An unusual M1 electromagnetic transition connecting octupole and quadrupole vibrations in¹⁷⁹Hf

A detailed level scheme for¹⁷⁹Hf has been constructed on the basis of extensive (n, γ), (d, p) and (d, t) data. The low lying levels are grouped into 15 rotational bands of which 14 are classified by Nilsson quantum numbers or vibrational configurations. One of the most interesting results concerns a dominant transition matrix element which connects an octupole vibration built on the 1/2[510] Nilsson orbit with a quadrupole vibration built on the 9/2⁺ [624] Nilsson ground state. A simple interpretation of this unusual decay mode is offered in terms of microscopic wave functions for the vibrational states. This interpretation leads to reasonable estimates for E1 hindrance factors from the octupole vibration to lower lying quasi-particle levels.