Fragmentation in dissipative collisions: a computer model study

Qualitative aspects of multifragmentation in atomic, molecular or nuclear collision processes are studied by means of a simple chain model, i.e., the collision of two chains of particles is analyzed and the possible reaction channels are determined. It is shown that the introduction of dissipative in addition to conservative forces increases the spectrum of possible reactions considerably. It leads to a large variety of fragmentation channels as they are observed experimentally. In this way, dissipative forces may give rise in mechanical systems to structure formation processes which are absent if exclusively conservative forces act between the particles. Moreover, it is shown that reaction patterns obey quite different features depending on whether symmetric collisions (similar masses of target and colliding chain of particles) or asymmetric collisions are considered (for the same initial values of the energy per particle taking part in the collision process). With increasing symmetry, the variety of possible reaction channels increases, in general. In addition, by introducing and increasing the strength of repulsive long-range (Coulomb) forces, the variety of possible reaction channels increases further. The possible fragment size distributions are compared with results obtained by statistical (probabilistic) fragmentation approaches. As it seems, at least for the simple model considered here, the dynamics and not the statistical properties determine the outcome of the fragmentation process.