La réaction de transfert avec des ions lourds

Abstract

The neutron transfer process in heavy-ion reactions is treated in accordance with Coulomb T-matrix (CTM) theory. On the basis of the Greider formalism, formulae giving differential and total cross sections in absolute magnitude are derived. Stress is laid upon appropriate normalization and nuclear structure considerations. The off-energy-shell contributions to the Coulomb T-matrix are therein treated in first approximation, resolving the originally incorrect energy dependence of the cross sections. The calculated angular distributions and excitation functions are in good agreement with the available data for energies well below the classical Coulomb barrier. Reduced widths are determined in good agreement with those derived on the assumption that a square potential well binds the transferred neutron to each of the heavy nuclei. The formalism is throughout compared with commensurate expressions derived from a DWBA treatment of the reaction. The CTM results are also applied to a case involving transfer of angular momentum along with the neutron; the theoretical predictions are compared with recent experimental data. For energies in the vicinity of the top of the Coulomb barrier, an attempt to integrate the transition amplitude analytically is described. This makes use of a simple cut-off model to account for the effects of absorption due to the nuclear potentials; although the angular distributions tally with measured values, the model proves inadequate to reproduce the observed magnitudes and energy dependence of the absolute cross sections.