Transitions in nuclear disassembly as viewed by fragment charge correlations.

Abstract

Central heavy-ion collisions in the (nearly) symmetric entrance channels {sup 20}Ne+{sup 27}Al, {sup 40}Ar+{sup 45}Sc, {sup 87}Kr+{sup 93}Nb, and {sup 129}Xe+{sup 139}La have been systematically studied at many intermediate beam energies. The relative sizes of the three largest fragments in the central events are studied using new variables defined from charge Dalitz plots. Autocorrelations between these variables and the method used to select the central events are investigated. Also described are the hidden constraints on these variables that are imposed by definition. For increasing beam energies, the average values of these variables imply transitions from sequential binary disassembly to multifragmentation at beam energies of {similar_to}50 and {similar_to}30 MeV/nucleon in the {sup 40}Ar+{sup 45}Sc and {sup 129}Xe+{sup 139}La entrance channels, respectively. Similar trends are observed for the central {sup 20}Ne+{sup 27}Al and {sup 87}Kr+{sup 93}Nb reactions.