TIME-SCALE FOR MULTIFRAGMENTATION IN INTERMEDIATE-ENERGY HEAVY-ION REACTIONS

Fragment-fragment correlations are used to probe the spatial-temporal extent of the emitting source in central Ar-36+Au-197 reactions at E/A =35, 50, 80, and 110 MeV. The experimental two particle correlations a re compared both with the Koonin-Pratt two-body formalism as well as a three-body Coulomb trajectory calculation. The spatial-temporal exten t of the emitting system decreases with increasing incident energy. Wi thin the context of a three-body Coulomb trajectory model the mean fra gment emission time rises sharply as a function of the assumed density of the system until rho/rho(0) approximate to 0.3. If one assumes a f ixed density, the extracted mean emission time decreases with increasi ng assumed charge of the emitting system. Assuming rho/rho(0) approxim ate to 0.3 the mean emission time tau according to calculations using: a three-body Coulomb trajectory model, is approximate to 115-135 fm/c at E/A=50 MeV and approximate to 75-100 fm/c at E/A=110 MeV. Comparis ons with a generalized N-body Coulomb trajectory model demonstrate tha t the effect of interactions with other emitted particles is negligibl e. The prediction of a microcanonical model which includes pre-emissio n correlations between the fragments is compared to the measured corre lation function at E/A=110 MeV.