Dynamical and statistical properties of hot nuclei

Properties of medium mass nuclei having excitation energies of 1.5 to 6 MeV/u have been probed in measurements of the multiplicities and energy spectra of emitted particles and fragments. The particle spectra indicate a progressive reduction of both the level density parameter, a, and the emission barriers as the excitation energy is increased. The evolution of the dominant de-excitation modes, observed with increasing excitation energy, is found to be qualitatively consistent with the predictions of statistical models. There is, however, evidence that dynamics may play an important role in fragment emission processes. At energies of 6 MeV/u multifragment emission is an important process. Varying theoretical models predict such multifragment events but differ in their predictions of the probability of such events.