Towards limiting temperatures in nuclei

Gamma-rays emitted from hot nuclei with mass around 115 and excitation energies between 350 and 550 MeV, formed in the 36Ar+90Zr reaction at 27 MeV/u, have been measured. The γ-ray yield from the decay of the giant dipole resonance in these nuclei remains constant over the excitation energy range studied. This quenching of the γ multiplicity cannot be explained by a continuous increase with temperature of the width of the resonance. Better agreement with the data is obtained by assuming a cut-off of γ-emission from the resonance above an excitation energy of 250 MeV. The existing data do not show entrance channel effects. (authors). 21 refs., 3 figs., 1 tab