Intense sources of ${}_{}{}^{246}{}_{}{}^{}\mathrm{Pu}$ have been produced (through double neutron capture by ${}_{}{}^{244}{}_{}{}^{}\mathrm{Pu}$) for making detailed electromagnetic and conversion-electron measurements of the decay of ${}_{}{}^{246}{}_{}{}^{}\mathrm{Am}_{}^m{}_{}{}^{}$ to levels of ${}_{}{}^{246}{}_{}{}^{}\mathrm{Cm}$. $\gamma$ rays from ${}_{}{}^{246}{}_{}{}^{}\mathrm{Pu}$ decaying to ${}_{}{}^{246}{}_{}{}^{}\mathrm{Am}$ levels were identified in a chemical milking experiment. Of the 260 ${}_{}{}^{246}{}_{}{}^{}\mathrm{Cm}$ $\gamma$ rays observed, 97 are new and 64 have been assigned multipolarities from Si (Li) conversion-electron measurements. Some transitions were found to have strong $E0\mathrm{}$ components, and two pure $E0\mathrm{}$ transitions were observed. High-resolution $\gamma -\gamma$-time coincidence measurements were used to establish 54 levels, from which the low-energy band structure of ${}_{}{}^{246}{}_{}{}^{}\mathrm{Cm}$ was determined. The investigation confirmed previous assignments of $K^{\pi }=0^{-}, 1^{-}, \mathrm{and} 2^{-}$ octupole bands, and a $K^{\pi }=0^{+}$ band at 1175 keV. We have also identified the probable $K^{\pi }=3^{-}$ octupole band, and a second $K^{\pi }=0^{+}$ band at 1289 keV. The two $K^{\pi }=0^{+}$ bands are discussed in terms of possible collective excitations. Other identified bands are discussed in terms of two-quasiparticle and multipole-phonon excitations.

RADIOACTIVITY ${}_{}{}^{246}{}_{}{}^{}\mathrm{Am}_{}^m{}_{}{}^{}$ (from $\beta$ decay of ${}_{}{}^{246}{}_{}{}^{}\mathrm{Pu}$ produced by double neutron capture on ${}_{}{}^{244}{}_{}{}^{}\mathrm{Pu}$); measured $E_{\gamma }$, $I_{\gamma }$, $\gamma \gamma$ coin, $I_{\mathrm{ce}}$; deduced levels, $J$, $\pi$, $log\mathrm{ft}$.

• Received 23 June 1975

DOI:https://doi.org/10.1103/PhysRevC.13.771