Neutron-Rich Nuclei Beyond {sup 132}Sn: Spherical Shapes and Octupole Correlations

Nuclear properties of nuclei with a few valence nucleons outside the doubly-magic {sup 132}Sn core and located in the octupole correlation region have been investigated via gamma-gamma-gamma coincidence measurements of prompt gamma-ray emitted in the spontaneous fission of {sup 252}Cf with Gammasphere. The high spin level scheme of {sup 134}I has been identified for the first time. Shell model calculations reproduce the level scheme quite well. The level schemes of {sup 137}I and {sup 139}Cs have been reinvestigated and extended. Their nuclear structure is well described by realistic shell model calculations. The g-factors of the 4{sup +} state in {sup 134}Te, 15/2{sup +} state in {sup 135}I, and 15/2{sup -} state in {sup 137}Xe were determined using a newly developed program for angular correlation analysis. The measured g-factors compared favorably with shell model calculations. Octupole correlations are proposed in {sup 141}Cs and {sup 142}Cs. The variations of D{sub 0} in the Cs isotopes exhibit a pronounced drop of dipole moment with increasing neutron number.