Interplay of mean field and nucleon–nucleon interactions in the production of carbon fragments in 16O induced reactions at incident energies up to 25 MeV/amu

Two different reaction mechanisms (which both occur at very short interaction times) contribute to the emission of intermediate mass fragments in reactions induced by a light nucleus such as 16O. They are the binary fragmentation of the projectile and the coalescence of nucleons during the course of the nucleon-nucleon interaction cascade which starts as soon as the two ions (or part of them) come into contact. These two mechanisms are easily distinguished from each other because their contributions to measured emission spectra have different energy dependence, the first peaking at an energy not far from that corresponding to the beam velocity, the other to a much smaller energy about equal to the Coulomb barrier between the observed fragment and an heavy residue with mass and charge near to those of the target nucleus. These features are clearly observed in the spectra of carbon fragments produced in the interaction of 16O ions with 59Co and 93Nb at incident energies between 100 and 400 MeV. In this paper we discuss these reaction mechanisms and suggest a theoretical interpretation which satisfactorily reproduces the experimental results.