LIFETIME MEASUREMENTS OF STRONGLY DEFORMED ROTATIONAL BANDS IN PM-133

We have measured lifetimes and deduced deformation parameters for rota tional bands in Pm-133 by the Doppler-shift attenuation method. A stro ngly coupled band based on the configuration with a hole in the g(9/2) orbital has deformation parameter beta(2)=0.40 (5), which is comparab le to or larger than typical superdeformed bands in the A similar to 1 30 region. We observe this band in Pm-133 down to its I=K=9/2 bandhead . Calculations with a configuration-dependent shell correction to the cranked Nilsson potential can explain the existence of such low-spin s uperdeformed structures in the A similar to 130 region. These shapes, which also occur in Pr-129,Pr-131, can be observed experimentally beca use of relatively low-lying shell gaps for beta 2=0.4 near Z=58, N=72. No high-spin intruder orbitals (upsilon i(13/2)) are occupied (over t he spin range observed), however the strongly deformation-driving prop erties of a hole in the extruder pi g(9/2) orbital appear to be an ess ential ingredient in lowering the energy of the superdeformed shape.