DEPENDENCE OF INTERMEDIATE-MASS FRAGMENT PRODUCTION ON THE REACTION-MECHANISM IN LIGHT HEAVY-ION COLLISIONS AT INTERMEDIATE-ENERGY

The same hot nuclear system (Sigma Z=18) has been studied for two diff erent entrance channels with reaction products detected in a forward a rray of scintillators: central collisions of Mg-24 on a C-12 target at 25A and 35A MeV and peripheral pickup reactions of Cl-35 on a Au-197 target at 43A MeV. The detection-efficiency-corrected charge distribut ions, multiplicity of charged particles and cross sections as a functi on of excitation energy are compared. The reaction mechanism is invest igated, through comparison to simulations with statistical observables . The central reaction Mg-24+C-12 at 35A MeV is well characterized by a dissipative binary collision scenario. Data at 25A MeV show less evi dence of such dynamical characteristics. The intermediate-mass fragmen ts (3 less than or equal to Z less than or equal to 8) production for each reaction is compared to model calculations for different values o f excitation energy. The systems formed in the central collision at 25 A MeV and the pickup reaction at 43A MeV show similar source character istics, both statistically and in momentum space. However, the yields of the various exit channels, from evaporation and/or fission to multi fragmentation and vaporization, differ for the two reactions.