Quadrupole moments of collective structures up to spin ～ 65 ? in 157Er and 158Er: A challenge for understanding triaxiality in nuclei

摘要

The transition quadrupole moments,Qt, of four weakly populated collective bands up to spin～65?in157,158Er have been measured to be～11?ebdemonstrating that these sequences are associated with large deformations. However, the data are inconsistent with calculated values from cranked Nilsson–Strutinsky calculations that predict the lowest energy triaxial shape to be associated with rotation about the short principal axis. The data appear to favor either a stable triaxial shape rotating about the intermediate axis or, alternatively, a triaxial shape with larger deformation rotating about the short axis. These new results challenge the present understanding of triaxiality in nuclei.