Signals for the transition from liquid to gas in hot nuclei
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Hot nuclei produced in 5-15 GeV proton-, pion-and antiproton-induced reactions on 197Au have been studied with the Indiana Silicon Sphere (ISiS) charged-particle detector array at the Brookhaven AGS accelerator. Each event has been reconstructed from the data to determine the excitation energy, charge and mass of the emitting source. Using E*/A as a sorting variable, the IMF kinetic energy spectra have been examined to assess the degree of thermal expansion in these reactions. Relative to SMM and SIMON-explosion calculations, the data suggest a weak extra thermal expansion energy above E*/A 5 MeV. IMF-IMF correlation functions show an order-of-magnitude decrease in the relative emission time in the interval E*/A 2-5 MeV. Above this value, a constant limiting time of 20-50 fm/c is found. These observations are consistent with the transition from liquid to vapor due to thermal heating.