Vibrational modes in 232Th from heavy-ion Coulomb excitation

The gamma spectrum coincident with the scattered particles in Coulomb excitation of 232Th by 450-MeV Kr ions is shown first. Then the moments of inertia of the ground and octupole bands are ploted in the usual way as a function of the square of the rotational frequency to display the backbending behavior. The apparent increase of the moments of inertia in the negative-parity bands, with respect to the ground-state band, arises from the strong Coriolis coupling between the K = 0- - 3- states of the octupole multiplet, leading to the concentration of the B(E3) strength on the lowest octupole band. Ratios of E2 transition energies of the negative-parity and ground-state bands are shown. The level energies of the ground-state band, as well as the K = 0-, K = 0+, K = 2+ side bands, are tabulated. The results are also summarized in a plot of moments of inertia vs (h-bar ω)2. 4 figures, 1 table