Collective potential-energy surfaces in heavy-ion reactions

Abstract

Multidimensional potential-energy surfaces have been calculated for heavy-ion reactions as a function of separation (or elongation), neck-formation and mass-asymmetry collective degrees of freedom. The reactions Ar + Ag, Kr + Cu, Kr + Bi and Xe + Bi, of current interest, are considered as examples. The effects of the entrance channel asymmetry and the total charge and angular momentum of the system are studied in detail, using the rotational liquid-drop model in an asymmetric twocenter parameterization of nuclear shapes. Several aspects of these multidimensional energy surfaces are investigated : The fusion-fission process, the fusion barriers, the saddle-point shapes and implications for the reaction mechanisms involved. Systematics in the neck and mass-asymmetry degrees of freedom are deduced for the configurations of interest along probable collision paths. The results are also compared and contrasted with the one-dimensional picture of the potential energy as a function of the separation coordinate. Aside from the dynamical aspects of the problem, the variety of the reaction mechanisms involved in heavy-ion reactions can be traced in the topography of the potential-energy surfaces and can be reasonably understood in the collective approach considered.