Non-yrast low-spin states in the triaxially deformed nucleus Xe-123

The non-yrast states of Xe-123 have been investigated with the reaction Te- 123(He-3,3n) by means of in-beam gamma -spectroscopy using a setup of 6 Com pton-suppressed high-purity-germanium (HPGe) detectors. More than 130 new t ransitions establishing over 35 new levels were observed. gamma gamma angul ar correlations were analyzed to assign spins and parities to the low-lying states, and to determine the multipole mixing ratios of the gamma -transit ions. With this method 9 spin and parity assignments were made and 19 multi pole mixing ratios could be determined. Excitation energies of negative-par ity states and the branching ratios of their decays are compared with predi ctions of the Rigid Triaxial Rotor plus Particle model (RTRP). (C) 2001 Els evier Science B.V. All rights reserved.