Coulomb excitation of vibrational states in {sup 232}Th with {sup 16}O projectiles

Excited states in {sup 232}Th were populated by Coulomb excitation with 80 MeV {sup 16}O ions. Gamma-gamma coincidences were detected with the detector array YRAST Ball. The one-phonon quadrupole and octupole vibrations are most strongly excited. These vibrations are in {sup 232}Th, particularly favorable cases for a study of their couplings, due to the small energy spacings of the {beta} and {gamma} bands and the K{sup {pi}}=1{sup -} and 2{sup -} bands, respectively. The need for additional experimental information on the {gamma}-ray intensities and the location of members of the octupole-vibrational bands is emphasized. The higher-lying K{sup {pi}}=0{sup +} bands with bandheads at 1079 and 1352 keV proposed previously are observed and some conflicting properties of these bands are discussed. The interpretation of the 1352 keV 0{sup +} band as two-octupole-phonon vibration is not supported by our data. A level at 1054 keV, previously assigned as 2{sup +} or 2{sup -} level, is tentatively proposed to be the bandhead of a second-excited K{sup {pi}}=2{sup +} band. Our {gamma}{gamma} coincidence data establish that the unusually enhanced E2 transitions from a 2{sup +} level at 1554 keV to members of the {beta} and {gamma} bands proposed previously do not exist. (c) 2000more » The American Physical Society.« less