EVOLUTION OF COLLECTIVITY TO VERY HIGH SPINS IN YB-160

Lifetimes of Yb-160 yrast states at high rotational frequencies have b een measured by the Doppler broadened line shape technique. Excited st ates in Yb-160 were populated by the reaction Sn-120(Ca-44,4n)Yb-160 a t a beam energy of 200 MeV and the experimental measurements were carr ied out in the coincidence mode with an array of Compton-suppressed ge rmanium detectors. The results for the 24(+) to 32(+) yrast states led to values of the transition quadrupole moments similar to those obtai ned for the lower members (h omega less than or equal to 0.29 MeV) of the ground band in previous recoil-distance measurements. The trend of reducing Q(t) values found for the I=34(+) and 36(+) states are sugge stive of band termination. The results are discussed in the light of c urrent theoretical predictions.