Axial asymmetry in the IBA and an extensive new 0(6) region near A=130

Abstract

Although the IBA‐1 contains no solutions corresponding to a rigid triaxial shape, it does contain an effective asymmetry arising from zero point motion in a γ‐soft potential leading to a non‐zero mean or rms γ. In the Consistent Q Formalism (CQF) of the IBA, most results of a calculation depend only on one parameter χ. A relation will be established between χ and the effective asymmetry parameter γ. The relation between the asymmetry occurring naturally in IBA‐1 and the triaxiality arising from the introduction of cubic terms into the IBA Hamiltonian will be discussed. It will be shown that γ‐band energy staggering is a particularly sensitive indicator of the degree of γ rigidity. Finally, an extensive new region of 0(6) like Xe and Ba nuclei near A=130 will be discussed. Their remarkable similarity to Pt will be explored. Deviations from the strict 0(6) limit can be described in terms of the interplay of soft and rigid axial asymmetry and calculations will be presented that interpret the Xe, Ba and Pt isotopes in this way.