Near-barrier transfer and fusion of the systems33S +90,91,92Zr

Abstract

Double differential cross sections of all prominent transfer channels have been measured in the systems 338+9~ at two energies close to the nominal Coulomb barrier. In addition the fusion excitation functions of these systems have been measured below and around the barrier. The angular-and Q-distributions of the most important transfer reactions have been analysed in the framework of a simple semiclassical formalism. Particularly the two-nucleon transfer angular distributions exhibit strong multi step coupling effects which manifest themselves in reduced cross sections at large angles corresponding to close distances. From the angular distributions at forward angles, where a single step character of the transfer reaction can be assumed, approximate form factors have been extracted employing a first order perturbation theory. Within the uncertainties of a schematic coupled channels calculation the isotopic differences of the sub-barrier fusion enhancement can be understood on the basis of the isotopic differences of the transfer form factors and Q-values.

Correlations between nucleon transfer and fusion at near-barrier energies for the systems32S +100,101Ru and33S +90,91,92Zr

“…enhancements in sub-barrier fusion cross sections). The importance of such systems was demonstrated in the study [7] of 33S+9~ It was observed, in agreement with other studies [8], that the inelastic couplings 1) are responsible for only part of the asymptotic barrier shifts Di in the sub-barrier fusion cross sections, and 2) cannot explain the isotopic effects. Hence coupling to the quasi-elastic transfer channels was needed; the measured transfer cross sections allowed to extract the form factors used in CC calculations which, taking into account both inelastic and transfer channels, gave a rathe~ good description of the D~.…”

“…In the same work [7], a decrease is reported in the transfer angular distributions at backward angles steeper than the predictions of a semiclassical model, where the absorption probability was derived from the elastic scattering cross sections. The "missing" cross section (Aat) was interpreted as loss of transfer flux feeding more complex channels and/or fusion.…”

Fusion and quasi-elastic transfer in the systems58Ni+90,91,94Zr near the Coulomb barrier

“…where D is the distance of closest approach and N is another constant, known function of k. For more details about the adopted formulas see also [3].…”

“…The set-up for the transfer measurements is described in detail in [3]. The beam-like particles were detected with a TOF--AE--E telescope.…”

“…[1]); as observed also in many other laboratories. In the heavier systems 33S+Zr we have still [3] a coherent experimental and theoretical description of the fusion process, but a detailed analysis of the transfer data suggests the evolution of the reaction through more complex transfer channels.…”