High-spin properties ofEr164in the multiple band crossing region

Abstract

High-spin states in /sup 164/Er have been studied by using the /sup 150/Nd(/sup 18/O,4n..gamma..) and /sup 164/Dy(..cap alpha..,4n..gamma..) reactions and by multiple Coulomb excitation with /sup 136/Xe ions. Several positive-parity bands are excited, and two negative-parity bands have been identified. The previously reported backbending behavior of the yrast sequence is demonstrated to result from the intersection of the ground band (seen to spin 22/sup +/) with an even-spin ''superband'' observed from spins 12/sup +/ to 24/sup +/. The odd-spin yrast superband and the second lowest even-spin superband also have been observed. All the superbands have moments of inertia appreciably larger than the ground band. The observed intersection of these multiple superbands with the ..gamma.. band produces different backbending behavior and a staggering of the energies of the odd- and even-spin members of the ..gamma.. band. B(E2) values for transitions below and through the band intersection regions of both the ground band and ..gamma.. bands have been deduced from multiple Coulomb excitation yields. In addition, lifetimes have been measured for the ground band by the Doppler-broadened line-shape technique. The level energies and B(E2) values are consistent with weak interaction matrix elements ( approx. = 45 keV) between the intersecting bands. Themore » B(E2) values of the unperturbed band are found to obey the simple rigid-rotor relationship. The 7/sup -/ negative-parity band exhibits a normal rotational sequence, while the 5/sup -/ band exhibits a large odd-even staggering and a larger moment of inertia. Two-quasiparticle-plus-rotor model calculations indicate strong rotation alignment and reproduce the observed properties of the high-spin states for both the positive- and negative-parity bands in /sup 164/Er.« less