Study on deformation and shape coexistence for Pb-188

The deformation and shape coexistence in Pb-188 have been investigated in t erms of the Projected Shell Model. Comparing the experimental data with the calculated results, it is shown that three shape configurations of sphere (Z = 82 shell closure), oblate (two particle-two hole in proton h(9/2) orbi tal) and prolate (multi-particle-hole) coexist each other in the low-lying excited states and the prolate band exhibits a mixture between two kinds of multi-particle-hole configurations, which means that the neutron i(13/2) a lignment happens gradually in this case. The mixing is discussed and the mi xing coefficients are given. The oblate band structure is predicted and the 2(+) prolate state is estimated to be in the energy range of 804-880keV.