Search

Fusion evaporation cross-sections in reactions known for the phenomenon of fusion hindrance in coupled-channels calculations at energies far below the Coulomb barrier, fission reactions known for entrance-channel dependence, capture (equivalently, quasi-fission) crosssections in compound systems forming super-heavy nuclei and the fission-plus-fusion evaporation observed in the same reaction, are studied on the basis of the Wong's model and the dynamical cluster-decay model (DCM) of Gupta and Collaborators, using in both cases the deformation and orientation dependent nuclear proximity potential. The deformations up to hexadecapole and integrations over both in-plane (co-planar) and out-of-plane (non-coplanar) configurations in Wong model and only the "compact" configurations in DCM are allowed. The concept of "barrier modification" for below-barrier energies, and that of non-compound "quasi-fission" component at above-barrier energies, is explored for the proximity potential in both the models. Noting that ( l-summed) Wong model is a special case of DCM for the fragment pre-formation factor to be unity, it is more suitable for the capturer cross-sections, where the in-coming nuclei keep their identity, or the (total) fusion cross-sections, whereas in DCM the role of pre-formation factor is to give the various components (fusion-evaporation, fission and quasi-fission) of the fusion process. [ABSTRACT FROM AUTHOR]

A dynamical collective clusterization model, called ihe dynamical cluster-decay model, is developed for the decay of a hot and rotating compound nucleus formed in the low-energy heavy ion reactions. The model is a non-statistical description for the decay of a CN to light particles, intermediate mass fragments, fusion-fission and quasi-fission (equivalently, capture) processes, and hence is given as an alternative to the well known Hauser-Feshbach analysis (statistical evaporation code) and statistical fission models. The quasi-fission or capture is the non-CN contribution, determined empirically. The deformations and orientation degrees of freedom (for compact orientations) of the incoming nuclei and of out-going nuclei/fragments are also included. The model considers all decay products as dynamical mass motions of preformed fragments or clusters through the interaction barrier, thereby including structure effects of the CN explicitly. The only parameter of the model is the neck-length parameter, which is related to the total kinetic energy TKE(T) or effective Q-value Qeff(T) at temperature T of the hot CN. This parameter could also be defined in terms of the CN binding energy and ground-state binding energies of the emitted fragments. The model is so far applied to the decay of compound systems 48Cr* 56Ni*, 116,118,122Ba*, 164Yb*, 246Bk*, and 292114*, formed in various reactions at different incident center-of-mass energies. Both the cross sections and TKE or TKE are considered. For ground-state (spontaneous) decays, the model gives the phenomenon of exotic cluster radioactivity. [ABSTRACT FROM AUTHOR]