DEFORMATION OF LIGHT XENON ISOTOPES

Recently measured B(E2;0(1)(+) --> 2(1)(+)) values for the Light xenon (Z=54) isotopes show a marked increase in deformation as the neutron numbers approach the midshell value of N=66. At first sight, this beha vior is anomalous because the 2: level energies are nearly the same fo r these isotopes. Moreover, this increase is not readily explained by several nuclear models that assign single shells to valence protons an d neutrons. In particular, the single-shell asymptotic Nilsson model w ith current parameters seriously underpredicts the B(E2;0(1)(+) --> 2( 1)(+)) values for Xe-118(64), Xe-120(66), and Xe-122(68). On the other hand, several modem multishell models correctly predict these values. We examine the latter results more closely to find ways in which the single-shell asymptotic Nilsson model can be revised to correctly repr oduce the measurements. We also show that the B(E2;0(1)(+) --> 2(1)(+) ) values for Lighter (N<66) barium isotopes, when they are measured, w ill test the predictive power of existing systematics and modeling of quadrupole deformations in nuclei.