Studies of fragment emissions at forward and intermediate angles in 25MeV/u Ar-40+In-115 reaction

On the basis of the energy spectra, the angular and Z distributions of the fragments emitted at forward and intermediate angle region in 25MeV/u Ar-40 + Zn-115 reaction, the evolution of emission mechanisms of fragments with the emission angles of the fragments in the laboratory system and the charge numbers of the fragments is discussed. The model of modified quantum molecular dynamics(MQMD) is employed to investigate the angular and Z distributions of the fragments. The theoretical calculations are in good agreement with the experimental data in general. But in the forward angles the yield of the fragments is underestimated by MQMD model while in the case of the intermediate: angle region, the calculated result is higher than the experimental data for the fragments whose charge numbers are in the vicinity of the projectile. The angular and charge distributions of the fragments are also compared with the statistical model of GEMINI. It is found that a small proportion of the statistical evaporation component exists in the forward angle region while in the intermediate angle region, this statistical evaporation component shows a Little increase. With the decrease of the fragment charge number, the non - equilibrium intermediate - velocity component goes up step by step and plays a leading role while the equilibrium evaporation one diminishes gradually.