Decay ofPm149(53 hr)

The radioactive sources were obtained from neodymium oxide, enriched in ${\mathrm{Nd}}^{148}$, irradiated in the Argonne reactor $CP-5\mathrm{}$. After the 1.8-hr activity of ${\mathrm{Nd}}^{149}$ had decayed away, the 53-hr activity in ${}_{61}{}^{}{}_{}{}^{}\mathrm{Pm}_{}^{149}{}_{}{}^{}$ remained. Some of the samples were purified by ion-exchange-column techniques before being studied. The radiations were investigated with a 180° focusing beta-ray spectrometer and the Argonne 256-channel scintillation coincidence spectrometer. The magnetic spectrometer resolved two components of the beta spectrum at 1.064±0.008 and 0.784±0.010 Mev. The beta rays were also studied by coincidence absorption techniques. In addition to the branch with a maximum energy of 0.784±0.010 Mev, this method revealed two more at 0.47±0.04 and 0.19±0.04 Mev. The scintillation pulse-height spectrum of the gamma rays revealed the presence of three transitions at 0.850±0.008, 0.582±0.006, and 0.285±0.001 Mev. A fourth gamma ray with an energy of 0.548±0.006 Mev was found in coincidence measurements. These radiations are fitted into a decay scheme comprising the ground state and four excited states in ${\mathrm{Sm}}^{149}$ at 0.285, 0.582, 0.833, and 0.850 Mev. The $log-ft$ values, transition intensities, and possible spin and parity assignments are discussed.