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

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 $^{20}\mathrm{Ne}+\phantom{\rule{0.16em}{0ex}}^{58,60,61}\mathrm{Ni}$ 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 $\mathrm{\ensuremath{\Delta}}E\text{\ensuremath{-}}E$ methods. A measurement of the angular distribution of $\ensuremath{\alpha}$ stripping in the $^{20}\mathrm{Ne}+\phantom{\rule{0.16em}{0ex}}^{61}\mathrm{Ni}$ system was performed using a gas $\mathrm{\ensuremath{\Delta}}E\text{\ensuremath{-}}E$ telescope.Results: For all three systems studied: $^{20}\mathrm{Ne}+\phantom{\rule{0.16em}{0ex}}^{58}\mathrm{Ni},\phantom{\rule{0.16em}{0ex}}^{60}\mathrm{Ni}$, and $^{61}\mathrm{Ni}$ total (sum of all transfer channels) cross sections are similar and dominated by $\ensuremath{\alpha}$ stripping.Conclusions: The results, as well as coupled reaction channel calculations, suggest that transfer is not responsible for smoothing the barrier height distribution in $^{20}\mathrm{Ne}+\phantom{\rule{0.16em}{0ex}}^{61}\mathrm{Ni}$, supporting the hypothesis that barrier distribution shapes are influenced by noncollective excitations.