Evidence for particle–hole excitations in the triaxial strongly-deformed well of 163Tm

Two interacting, strongly-deformed triaxial (TSD) bands have been identified in the Z=69 nucleus {sup 163}Tm. This is the first time that interacting TSD bands have been observed in an element other than the Z=71 Lu nuclei, where wobbling bands have been previously identified. The observed TSD bands in {sup 163}Tm appear to be associated with particle--hole excitations, rather than wobbling. Tilted-axis cranking (TAC) calculations reproduce all experimental observables of these bands reasonably well and also provide an explanation for the presence of wobbling bands in the Lu nuclei, and their absence in the Tm isotopes.