Low-spin termination of the superdeformed band inNd135

The decay of the superdeformed (SD) band in ${}_{}{}^{135}{}_{}{}^{}\mathrm{Nd}$ was studied with the early implementation of gammasphere. The results suggest that the SD band ‘‘terminates’’ at spin 25/2. This termination is explained by a change of the SD minimum toward a triaxial lower deformation. Ultimate cranker calculations with the ${\mathit{i}}_{13/2}$ orbital occupied relate this change to a shift of a proton and neutron pair out of deformation-driving Nilsson orbitals. This is a completely new and unexpected mechanism for the decay of SD bands.