Collective mode in nuclei: Progress in the study of the gamma decay of the giant dipole resonance

The study of the gamma decay of the giant dipole resonance (GDR) has allowed to investigate nuclear structure properties at excitation energies up to the Fermi energy. It continues to be a useful tool to explore the basic nuclear properties at finite temperature and angular momentum, such as nuclear shapes and thermal effects. In particular, the dependence of the GDR width as a function of temperature and angular momentum provides information on the evolution of the nuclear shapes and of the damping mechanisms of this collective state. This is an interesting topic under discussion which is presently addressed with new and more exclusive measurements. In reviewing the activity in this field selected exclusive data concerning the extreme region of temperature and angular momentum will be presented. In particular data for the two mass regions A=120-130 and A=180-200 will be discussed, with results based on measurements made at the INFN laboratories LNL using the HECTOR and GARFIELD arrays.