Temperatures in heavy ion reactions: Simulation via quasiparticle dynamics

The observation of different temperatures obtained in heavy-ion reactions by measuring kinetic energy distributions (kinetic temperatures) or abundances of different species (chemical temperatures) is addressed by means of a computer simulation based on the quasiparticle dynamics model. The simulations qualitatively agree with experiment: For both ⁴He and ⁶Li nuclei emitted in intermediate-energy heavy-ion reactions, the chemical temperature is found to be in the 3±{}1 MeV range, much lower than the kinetic temperature. Further, we do not find a strong variation of the chemical temperatures over the laboratory bombarding energy range of 35A to 100A MeV. The difference in the two temperatures is found to be established after a fairly short time scale roughly corresponding to the breakup time of the reaction region.