Correlations of intermediate mass fragments from Fe+Ta, Au, and Th collisions.

Abstract

Charge, velocity, and angular correlations between intermediate mass fragments (IMF) are presented for 50 and 100 MeV/nucleon Fe bombardments of Ta, Au, and Th targets. Correlation functions generated as a function of the relative velocity and the opening angle between two IMF's are qualitatively independent of the projectile energy and target mass and show a suppression at small relative velocities and opening angles due to the Coulomb repulsion between the fragments. The correlations are consistent with IMF's emitted primarily from a highly excited target residue following a rapid preequilibrium cascade. The correlation data are compared to model calculations using the event generator meneka and the quantum molecular dynamics (QMD) code with a statistical deexcitation of residual fragments utilizing the multifragmentation code smm. All data are consistent with a simultaneous multifragmentation at a freeze-out density of 0.1--0.3 times normal nuclear matter density or a more sequential emission with time constant \ensuremath{\tau}\ensuremath{\le}500 fm/c.