SUPERDEFORMATION IN ER-154

A superdeformed (SD) band consisting of 13 gamma-ray transitions has b een observed in Er-154, an isotone of Dy-152(66). The experiment was p erformed using the Sn-118(Ar-40,4n) reaction at E(Ar-40)=185 MeV and t he early implementation of GAMMASPHERE. This is an observation of a SD band in the A approximate to 150 region with a proton number greater than 66. The J((2)) moment of inertia of the band is constant above ($ ) over bar h omega=0.45 MeV and shows a sharp rise below this value su ggesting a paired band crossing. These results suggest that total Rout hian surface calculations fail to accurately predict the deformation o f the band.