Levels inSm149from the Decay ofEu149andPm149

The levels in ${}_{}{}^{149}{}_{}{}^{}\mathrm{Sm}$ were studied by means of the radioactive decay of ${}_{}{}^{149}{}_{}{}^{}\mathrm{Pm}$ and ${}_{}{}^{149}{}_{}{}^{}\mathrm{Eu}$. Sources of these isotopes were obtained from the decay of the parents ${}_{}{}^{149}{}_{}{}^{}\mathrm{Nd}$ and ${}_{}{}^{149}{}_{}{}^{}\mathrm{Gd}$. Gamma-ray spectra were measured with NaI(Tl) and Ge(Li) spectrometers, and electron spectra were determined with a surface-barrier silicon detector. Gamma-gamma coincidence spectra were obtained with NaI(Tl) and Ge(Li) detectors in conjunction with a multiparameter analyzer. Decay schemes are proposed which have levels in ${}_{}{}^{149}{}_{}{}^{}\mathrm{Sm}$ at 22.5, 277.0, 285.9, 350.0, 528.5, 558.4, 590.9, 636.4, 830.4, 833.2, and 881.9 keV. Fourteen gamma-ray transitions are observed in the decay of ${}_{}{}^{149}{}_{}{}^{}\mathrm{Eu}$, and twenty-five are observed in that of ${}_{}{}^{149}{}_{}{}^{}\mathrm{Pm}$. All of these transitions fit into the proposed level structure. Multipolarities are assigned from conversion-coefficient data for transitions of $254 \mathrm{}\left(M1\mathrm{}\right)\mathrm{}$, $277 \mathrm{}\left(M1\mathrm{}\right)\mathrm{}$, $327 \mathrm{}(M1+E2\mathrm{})\mathrm{}$, $350 \mathrm{}\left(E2\mathrm{}\right)\mathrm{}$, $505 \mathrm{}\left(E2\mathrm{}\right)\mathrm{}$, $528 \mathrm{}\left(E2\mathrm{}\right)\mathrm{}$, $535 \mathrm{}\left(E2\mathrm{}\right)\mathrm{}$, and 558 keV ($E2\mathrm{}$).