THERMAL AND QUANTAL FLUCTUATIONS AS PROBED BY THE GDR OBSERVABLES

A study of the strength function and of the angular distribution of the gamma rays from the giant dipole resonance in hot rotating Sn nuclei is presented. The two GDR observables (spectrum and angular distribution) were measured at the nuclear temperature T approximately 2 MeV for several different angular momentum intervals of the compound nucleus. The data were obtained with the HECTOR detector array that includes a 38 element multiplicity filter. Data are compared to model predictions of adiabatic thermal fluctuations of shape and orientation angles. A satisfactory agreement is found with the exception of the angular anisotropy at the higher rotational frequencies. The systematics of angular momentum dependence of the GDR width and of the a2(E(gamma)) suggests a constant spreading width at this temperature.