New Temperature Measurements in 197Au + 197Au Collisions

We report on new measurements of breakup temperatures for target spectators from 197Au + 197Au reactions at 1000 MeV per nucleon. The temperatures rise with decreasing impact parameter from 4 MeV for peripheral to about 10 MeV for the most central collisions, in good agreement with previous results for projectile spectators at 600 MeV per nucleon. The measured temperatures agree quantitatively with the breakup temperatures predicted by the statistical multifragmentation model. For these calculations a relation between the initial excitation energy and mass was derived which gives good simultaneous agreement for the fragment charge correlations. The energy spectra of light charged particles and the behaviour of the mean kinetic energies of neutrons indicate a substantial component of light particle emission prior to the final breakup stage.