QUANTAL AND THERMAL DAMPINGS OF GIANT-DIPOLE RESONANCES IN ZR-90, SN-120, AND PB-208

The damping of the giant dipole resonance (GDR) is studied in Zr-90, S n-120, and Pb-208 as a function of temperature T. The results show tha t the coupling of GDR to the pp and hh states is responsible for the i ncrease of the GDR width with increasing T up to 3 MeV and its saturat ion at higher T. The quantal width, caused by the coupling to ph excit ations, decreases slowly with increasing T. An overall agreement is fo und between the theoretical evaluations and the recent experimental da ta in heavy-ion fusion reactions and inelastic alpha scattering. At ve ry high T a behavior similar to the transition from zero to ordinary s ounds is observed.