Light-particle emission and heavy-residue formation in the fusion-like reactions 40Ar+ 40Ca at 15 MeV/u and 28Si+ 28Si at 20 MeV/u

Abstract

Heavy reaction products coincident with neutrons and light charged particles were studied in central collisions in the mass-symmetric systems 40Ar+ 40Ca and 28Si+ 28Si at incident energies of 15 respectively 20 MeV/u. The results demonstrate quantitatively an interrelation between heavy-residue mass and element distributions and light-particle multipicities: the mass difference between the observed fragments and the compound nuclei can be explained entirely by the emission of light particles with Z ⩽ 2. All neutron data are very well reproduced within the framework of a quantal phase-space model, stressing the importance of two-body collisions in the reaction dynamics already at these energies. Trends in the deduced nultiplicities and nuclear temperatures indicate evidence for a limiting excitation energy for residue formation.