Examining the cooling of hot nuclei

Energy spectra have been measured for helium and hydrogen isotopes emitted from highly excited residues produced in central Xe 1 Cu collisions at E/A530 MeV. The observed differences between the spectra for He and He nuclei can be attributed to the time dependent evaporative cooling of the residues. This cooling dynamics is also reflected in a characteristic dependence of isotope ratios on the kinetic energy of the emitted particles in reasonable agreement with present evaporative models. @S0556-2813~98!50302-0#