COMPETING PROTON AND NEUTRON ALIGNMENTS IN NEUTRON-DEFICIENT XE-NUCLEI

High-spin structures of the neutron-deficient Xe-117, Xe-118, Xe-120 isotopes have been studied by in-beam gamma-ray spectroscopic techniques. The final nuclei have been identified by means of charged-particle detectors. Collective rotational bands based on the neutron d5/2, 97/2 and h11/2 configurations have been identified in Xe-117. In the even Xe-118 and Xe-120 nuclei several new side bands were observed and the previously known bands were extended. The present level schemes include two positive-parity bands constructed to high spin in Xe-118, whereas in Xe-120 three such bands were observed. In order to explain these bands, both proton and neutron (h11/2)2 alignments, as well as the shape degree of freedom, have to be invoked. The possible occurrence of a gammaS-band is addressed and a pronounced structural change for more heavy Xe-isotopes is discussed. All negative-parity side bands are interpreted in terms of proton two-quasiparticle excitations. The experimental data are compared with total routhian surface calculations.