HEAVY FRAGMENT PRODUCTION IN AR-40-232 REACTIONS AT 27A, 44A, AND 77AMEV(TH)

In the reactions Ar-40+Th-232 at 44A and 77A MeV heavy fragments (HF) are produced in events where a large fraction of the incident energy i s thermalized. These events are accompanied by, on the average, two in termediate mass fragments (IMF). The IMF's have various origins: evapo ration from a rather massive complex, projectile remnants, and from pa rtially damped collisions. It is concluded that the heavy fragments ar e formed in semicentral collisions with light particle and IMF emissio ns which reduce the mass and excitation energy of the residual system such that fission becomes improbable. The HF production is found to be low at 27A MeV.