Levels of 232U fed in 236Pu alpha decay.

Abstract

The \ensuremath{\gamma} spectrum following the \ensuremath{\alpha} decay of $^{236}\mathrm{Pu}$ has been reinvestigated with a high-resolution HPGe detector. Accurate energies and intensities are reported for 26 \ensuremath{\gamma} transitions, of which 20 were observed for the first time. A decay scheme is constructed using the Ritz combination principle, \ensuremath{\gamma}\ensuremath{\gamma} coincidence data, and previously known data from nuclear reactions and ${\mathrm{from}}^{232}$Pa ${\mathrm{\ensuremath{\beta}}}^{\mathrm{\ensuremath{-}}}$ decay. We observe feeding of the ground-state rotational band up to spin 8, the \ensuremath{\beta} vibrational band to spin 4, the K=0 octupole vibrational band to spin 5, and the bandhead of the \ensuremath{\gamma} vibrational band. New states of $^{232}\mathrm{U}$ at 927.3 and 967.7 keV, populated with low \ensuremath{\alpha}-decay hindrance factors, are assigned as members of a second-excited ${\mathit{K}}^{\mathrm{\ensuremath{\pi}}}$=${0}^{+}$ band. The ratio of E1/E2 transitions in the decay of these states suggests that the E1 transitions to members of the K=0 octupole band may be rather fast (\ensuremath{\approxeq}${10}^{\mathrm{\ensuremath{-}}3}$ Weisskopf units). Systematics of hindrance factors for \ensuremath{\alpha} decay to vibrational states are presented.