TEMPERATURE AND EXCITATION-ENERGY OF HOT NUCLEI IN THE REACTION OF AR-40-197 AT 25 MEV(AU)NUCLEON/

The coincidence measurements between heavy fission fragments and light charged particles with Z less than or equal to 2 were carried out for the Ar-40 + (197)AU reaction at 25 MeV/nucleon, to study the properti es of hot nuclei in heavy ion induced reactions, The linear momentum t ransfers (LMTs) were deduced from the folding angle and the time-of-fl ight difference between two fission fragments of heavy residues. The r elationship of the nuclear temperature (slope parameter of the energy spectrum) and the excitation energy was determined independently from the measurement of the kinetic energy spectra in the frames of the emi tting sources and from the LMT analysis. Both the temperature and the excitation energy increase with decreasing impact parameter, which sug gests that a plateau temperature of 5.5 MeV is reached at an excitatio n energy of 3.1 MeV/nucleon. The result was also compared with various statistical models that explain the plateau by the multifragmentation process, where the excitation energy is assumed to be stored in compr ession and expansion effects. (C) 1997 Elsevier Science B.V.