Shape co-existence in Yb-157

The excited states of Yb-157 have been studied in the (SM)-S-144(O-16 3n) reaction at O-16 energy of 90MeV using techniques of in-beam gamma-ray spectroscopy. The level scheme for Yb-157 was established based on the measured results of gamma-gamma coincidences, gamma-ray anisotropies and DCO ratios. The level scheme is dominated by two parallel de-exciting sequences with different characteristics, which correspond to collective rotation and single particle excitations, respectively. This shape co-existence, as well as the structural evolution of the yrast vi(13/2) band with increasing angular momentum,have been discussed briefly.