Radioactive Decay ofYb177

The decay characteristics of the 1.8-hr negatron emitter ${\mathrm{Yb}}^{177}$ have been investigated by means of betaray and gamma-ray coincidence scintillation spectrometers. Gamma rays of energies 0.118, 0.140, 0.147, 0.95, 1.09, 1.12, and 1.24 Mev are found to accompany the decay. The gamma-ray energy and intensity data can be satisfied by postulating excited levels in ${\mathrm{Lu}}^{177}$ at 0.118, 0.147, 0.287, and 1.24 Mev. Beta-gamma coincidence scintillation spectrometer studies indicate that the 0.118-, 0.147-, and 1.24-Mev levels as well as the ground state of ${\mathrm{Lu}}^{177}$ are directly populated by beta decay from ${\mathrm{Yb}}^{177}$. Tentative spin and parity assignments for the excited levels of ${\mathrm{Lu}}^{177}$ are presented.