IN-BAND M1 AND E2-TRANSITION RATES AND COLLECTIVE STRUCTURES IN BA-128

Subpicosecond mean lifetimes of eight excited states in Ba-128 populat ed via the Zr-96(S-36,4n) reaction were measured by the Doppler-shift attenuation (DSA) technique using a line-shape analysis. The different ial decay-curve method (DDCM) was applied for the lifetime determinati on. The B(E2) values in the yrast band indicate that the first band-cr ossing is with a proton S-band. The configuration pi h(11/2)d(5/2) Of the negative-parity semi-decoupled bands is confirmed by the measured B(E2, I --> I - 2) and B(M1, I --> I --> 1) transition strengths. The higher-lying ''dipole'' band in Ba-128 can be described as a high-g fo ur-quasiparticle band built on the prolate configuration (pi h(11/2)d( 5/2)) X (nu h(11/2)g(7/2)) (C) 1998 Elsevier Science B.V.