Production and deexcitation of hot nuclei in collisions of 27 MeV/nucleon 40Ar with 238U

Abstract Hot nuclei, produced in the reaction 1080 MeV 40 Ar+ 238 U, have been studied by means of the light charged particles emitted in coincidence with fission fragments. A dominant fraction of the light charged particles emitted in the backward hemisphere (60%, 75%, 80% and 85% for 1,2,3 H and 4 He, respectively) comes from evaporation from a composite nucleus prior to scission. Careful analysis of the cross sections and energy spectra of these evaporated particles yields several properties of the hot nuclear emitters: (i) they are thermalized with an average temperature of 4.0–4.6 MeV, (ii) they are quite deformed (mean axis ratio ≈ 2 1 ) and are rapidly spinning ( J r.m.s. of 100–140 h MeV ). Predictions from a dynamical model, based on the Landau-Vlasov equation, are consistent with the experimental results, and give insights into the time evolution of the fused system