Giant Dipole Resonance in the Hot and Thermalized 132Ce Nucleus: Damping of Collective Modes at Finite Temperature

The gamma decay of the giant dipole resonance (GDR) in the 132Ce compound nucleus with temperature up to about 4 MeV has been measured, using the reaction 64Ni + 68Zn at Ebeam = 300, 400, and 500 MeV. The gammas and charged particles measured in coincidence with recoils are consistent with a fully equilibrated compound nucleus emission. The GDR width, obtained with the statistical model analysis, is found to increase almost linearly with temperature. This increase is rather well reproduced within a model including thermal shape fluctuations and the lifetime of the compound nucleus.