Quasielastic transfer in the 136 X e + 64 Ni reaction

Single and multinucleon transfer yields for the ${}^{136}{\mathrm{X}\mathrm{e}+}^{64}\mathrm{Ni}$ reaction at a scattering energy $\ensuremath{\approx}5%$ above the Coulomb barrier energy are studied using particle\char21{}\ensuremath{\gamma}-ray coincidence data. $Q$-value and scattering-angle distributions are extracted for the stronger channels. A fast transfer mechanism dominates the yields to these channels over an extended $Q$-value range, leading to a concentration of the cross section near the grazing angle. Analysis of the angular distributions based on a semiclassical barrier penetration model suggests that the single-nucleon and two-neutron exchange channels are dominated, respectively, by direct and two-step sequential transfer from the ground or low-lying excited states of the participating nuclei. The multiproton transfer channels have angular distributions that indicate a more complex mechanism, although direct cluster transfer from an excited configuration cannot be fully discounted. In a separate analysis, the relative population of different mass channels is found to be in general agreement with the expectations of a ``random walk'' model of particle exchange.