Level Structure of Low-Lying Excited States ofGa66Populated by the Decay of 2.2-hGe66

The decay of 2.2-h ${\mathrm{Ge}}^{66}$ to levels in ${\mathrm{Ga}}^{66}$ has been investigated by the use of both singles and coincidence $\gamma$-ray spectroscopic techniques that made exclusive use of high-resolution Ge(Li) detectors. The internal-conversion electron spectrum was also studied. A total of 23 transitions was observed in this decay; these were incorporated in a complete and unambiguous level scheme that differs markedly from those previously proposed. The excitation energies of the states in ${\mathrm{Ga}}^{66}$ found to be populated in this decay are 43.8, 108.9, 234.0, 290.9, 381.8, 514.6, 536.6, and 706.0 keV. The half-life of the ${\mathrm{Ge}}^{66}$ activity was redetermined to be be 2.23±0.10 h. The half-life of the first excited state was measured by delayed-coincidence techniques to be 21±2 nsec. The multipolarities of many of the transitions were determined. Spin and parity assignments of many of the excited states were inferred, and severe limitations could be imposed on the spin assignments of the remainder of the levels. The $log\mathrm{ft}$ values of all $\beta$ branches were established, and limits on the amount of isobaric-spin impurity present in the ground state of ${\mathrm{Ge}}^{66}$ were set. The level characteristics were found to be consistent with expectations derived from theoretical considerations.