Examination of the influence of transfer channels on the barrier height distribution: Scattering of 20Ne on 58Ni, 60Ni, and 61Ni at near-barrier energies

Abstract

Background: It was suggested that the shape of the barrier height distribution can be determined not only by strong reaction channels (collective excitations) but also by weak channels such as transfers and/or noncollective excitations. Purpose: The study of the barrier height distributions for the 20Ne + 58,60,61Ni systems requires information on transfer cross sections at near-barrier energies. Methods: A measurement of the cross sections for various transfer channels at a backward angle (142 degrees), at a near-barrier energy was performed. Identification of products was based on time-of-flight and E-E methods. A measurement of the angular distribution of α stripping in the 20Ne + 61Ni system was performed using a gas E-E telescope. Results: For all three systems studied: 20Ne + 58Ni, 60Ni, and 61Ni total (sum of all transfer channels) cross sections are similar and dominated by α stripping. Conclusions: The results, as well as coupled reaction channel calculations, suggest that transfer is not responsible for smoothing the barrier height distribution in 20Ne + 61Ni, supporting the hypothesis that barrier distribution shapes are influenced by noncollective excitations.