正 Hot nuclei produced in the reactions of 25 MeV/u40Ar with 209Bi andNa1Ag are studied.Theinitial properties of these nuclei :excitation energies,linear momentum transfer and temperatures are char-acterized through the measurements of folding angle of fission fragments,light charged particle energyspectra and intermediate mass fragments.Nuclei with excitation energies as high as~600 MeV and tem-peratures as high as~6 MeV are produced.The spectra of alpha particles detected in coincidence with fis-sion fragments in the case of different average linear momentum transfer are analyzed and the initial tem-peratures of the hot nuclei are determined.A saturation(or limiting)temperature near 6 MeV is foundfor alpha emission from medium mass nuclei having excitation energies higher than 3 MeV/u.This resultprovides evidence for a soft nuclear equation of state at thee high excitation energies and is consistentwith predictions of statistic multifragmentation model calculations.
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