OBSERVATION OF A SATURATION IN THE TIME-SCALE FOR MULTIFRAGMENT EMISSION IN SYMMETRICAL HEAVY-ION COLLISIONS

We have measured two-fragment reduced-velocity correlation functions of the intermediate mass fragments (IMF: 3 less-than-or-equal-to Z less-than-or-equal-to 7) produced in multifragment final states for the Kr + Nb system (E/A = 35, 45, 55, 65, and 75 MeV). From the measured correlation functions we extract mean IMF emission lifetimes (tau) which are observed to decrease from tau almost-equal-to 400 fm/c at E/A = 35 MeV to tau almost-equal-to 125 fm/c at E/A = 55 MeV. For beam energies in excess of E/A = 55 MeV, no further decrease in tau is observed, indicating a possible saturation of the mean emission lifetime for IMF produced in multifragment exit channels.