The radiations from ${\mathrm{Yb}}^{169}$ have been examined by means of a thin lens spectrometer and absorption-coincidence techniques. The half-life was found to be 33±1.5 days. The half-life of the metastable state was determined as 0.67 μ sec. ${\mathrm{Yb}}^{169}$ decays by electron-capture to ${\mathrm{Tm}}^{169}$. Eleven gamma-rays were observed in the photoelectron and internal conversion spectra determined with the spectrometer. On the basis of the absorption-coincidence and spectrometer data, two decay schemes are discussed.

• Received 18 December 1950

DOI:https://doi.org/10.1103/PhysRev.82.579