THE GIANT-DIPOLE RESONANCE BUILT ON HIGHLY EXCITED-STATES - RESULTS OF THE MEDEA-EXPERIMENT

Gamma-rays, light charged particles and evaporation residues emitted f rom hot nuclei formed in the Ar-36 + Zr-90 reaction at 27 MeV/u have b een measured with a nearly 4pi barium fluoride multidetector. It is sh own that hot Sn-like nuclei with a range of excitation energies betwee n 300 and 600 MeV are produced. The gamma-ray yield from the decay of the Giant Dipole Resonance in these nuclei is shown to remain constant over this excitation energy range. The measured gamma-ray spectra are compared with statistical calculations encompassing several recent th eoretical models for the quenching of gamma-ray emission from the dipo le resonance at very high temperatures.