The production, characterization and de-excitation of hot nuclei

A brief review of some experimental measurements of particle and γ-ray emission which have been used to probe the thermodynamic properties of highly excited nuclei, as well as certain statistical and dynamical aspects of their de-excitation, is presented. Significant decreases of the nuclear level density parameter with increasing excitation energy are indicated by spectral data. The onset of this decrease depends on the nuclear mass. A limiting temperature of 6.5 MeV for medium mass nuclei is observed. A critical temperature for semi-infinite nuclear matter near 17 MeV is derived from this limiting temperature, as well as from a preliminary analysis of residue excitation functions. Residues from highly excited heavy nuclei (A ∼ 250) are interpreted as resulting from the most central collisions in the reactions of 40Ar with 232Th and provide evidence for important dynamic effects in the de-excitation process. Evidence for the mass asymmetry dependence of dynamic delays is summarized and briefly discussed. (authors). 40 refs., 8 figs