The Decay Scheme ofCu66

The decay scheme of 5.2-minute ${\mathrm{Cu}}^{66}$ has been determined by beta-ray spectrometer, scintillation spectrometer, and coincidence measurements. It is found that 9.2±1 percent of the beta-ray transitions go to an excited state of ${\mathrm{Zn}}^{66}$ whose lifetime is less than ${10}^{-7\mathrm{}}$ second and are followed by 1.044±0.010-Mev gammarays. The remaining 91 percent of the beta-decays go to the ground state of ${\mathrm{Zn}}^{66}$, with an upper energy limit of 2.63 ±0.02 Mev. This high energy beta-group appears to have the allowed spectrum shape. Both beta-decays have $\mathrm{ft}$ values characteristic of allowed transitions. Spin and parity assignments for ${\mathrm{Cu}}^{66}$ and for the 1.044-Mev level of ${\mathrm{Zn}}^{66}$ are made, and some features of the decay of ${\mathrm{Ga}}^{66}$ to ${\mathrm{Zn}}^{66}$ are discussed.