Limiting excitation energies in fusion evaporation reactions

The mass dependence of the critical excitation energy above which a hot nucleus does not decay any more by particle evaporation, has been studied in the mass range 75 less than or equal to A less than or equal to 130. The experimental values of the critical excitation energy have been obtained by means of a new integral method based on the analysis of the widths of the evaporation residue mass distributions as a function of the residue velocity. The obtained mass dependence appears to be stronger than expected by Various models and a predicted dependence on the ZIA ratio of the decaying nucleus seems to be confirme