Hot rotating nuclei studied by the photon decay of the giant dipole resonance

A study of the spectral and angular distributions of the high energy gamma-rays emitted by the giant dipole resonance (GDR) in hot compound nuclei for the two mass regions A=110 and A=160-170 at a variety of excitation energies (E*=50-90 MeV) is presented. A comparison of the data with model predictions at the equilibrium deformation and with thermal fluctuations in the adiabatic limit is discussed. In general, the adiabatic calculations give a fair account of the data exception made for Sn at very high spins. In addition the combined analysis of the strength function and of the angular distribution suggests that large deformations caused by angular momentum effects are responsible of the width increase while collisional damping is constant at least up to T=2 MeV. (author). 16 refs., 9 figs., 1 tab