Rotation and shape changes in Tb151 and Pb196: Probes of nuclear structure and tunneling process in warm nuclei. I. Experimental analysis

The γ decay associated with the warm rotation of the superdeformed nuclei Tb151 and Pb196 has been measured with the Euroball IV array. Several experimental quantities are presented, putting strong constraints on the decay dynamics in the superdeformed well. The data are successfully reproduced using a Monte Carlo simulation of the γ decay based on microscopically calculated energy levels, E2 decay probabilities, collective mass parameters, and potential energy barriers between the wells associated with normal and super deformation. This allows one to test the basic ingredients of the physical process, such as the strength of the two-body residual interaction and the potential barriers as a function of spin and excitation energy. We also show that the data probe the E1 strength function, indicating an enhancement around 1-2 MeV γ rays, which might be related to octupole vibrations.