Shape coexistence in Pb-188

The shape coexistence in Pb-188 is investigated in terms of the projected s hell model. Analyzing the experimental data with the calculated results, it is shown that the three shapes, sphere, oblate and prolate, coexist with e ach other in the low-lying excited states. The prolate band exhibits a mixt ure between two kinds of multi-particle-hole configuration. The mixing is d iscussed and the mixing coefficients are given, meaning the vi(13/2) pair a lignment happens gradually in this case. The oblate (pi h(9/2)2p-2h) band s tructure is predicted and the 2 (+) prolate state is in the range of 804-88 0 keV.