The decay of ${}_{}{}^{156}{}_{}{}^{}\mathrm{Pm}$ has been studied resulting in the first detailed information on the excited states of ${}_{}{}^{156}{}_{}{}^{}\mathrm{Sm}$. About 25 levels were found, of which two were γ-decaying isomers. The expected low-lying quadrupole vibrational levels could not be identified. The observed decay rates for β and γ transitions have enabled the classification of some levels, including the β-decaying ground state of ${}_{}{}^{156}{}_{}{}^{}\mathrm{Pm}$, in terms of specific two-quasiparticle states. The total beta-decay energy of ${}_{}{}^{156}{}_{}{}^{}\mathrm{Pm}$ was obtained as 5.155(35) MeV.

• Received 29 January 1990

DOI:https://doi.org/10.1103/PhysRevC.41.2325