CONTRASTING BEHAVIOR IN OCTUPOLE STRUCTURES OBSERVED AT HIGH-SPIN IN RA-220 AND TH-222

Alternating-parity states connected by strong E1 transitions, characte ristic of a reflection-asymmetric rotor, have been observed to high sp ins in the isotones Ra-220 and Th-222. This level structure is observe d up to J(pi) = 29(-) (31(-)) in Ra-220 while it cannot be seen beyond J(+) = 24(+) (25(-)) in Th-222. These observations are consistent wit h Woods-Saxon-Bogolyubov cranking calculations which predict that the yrast band of Th-222 will undergo a shape transition at J = 24 HBAR, i n contrast to that of Ra-220 which maintains its reflection asymmetry to higher spins.