Dissipation by transfer and its influence on barrier distributions

The quasielastic barrier distribution (Dqe) of the ²⁰Ne +²⁰⁸Pb system exhibits a single broad structureless peak, unlike the results of coupled-channels calculations, including the strongest collective states of both projectile and target, which show a pronounced double-peaked structure. Separate measurements of the transfer strength, combined with the relatively small number of weak noncollective states in ²⁰⁸Pb, suggested that the observed barrier smoothing in this system could be due to the influence of couplings to transfer reactions. The coupled reaction channels (CRC) calculations performed by explicitly coupling to the two strongest transfer partitions, one-neutron pickup and one-proton stripping, suggest that the cumulative effect of coupling to many relatively weak transfer channels is responsible for the barrier smoothing rather than a few strong transfer reactions. In this perspective, the four main transfer channels (one- and two-neutron pickup and one-proton and one-alpha stripping) of the ²⁰Ne +²⁰⁸Pb system were coupled to the collective excitations by employing an upgraded ccqel code, where we introduced the dependence of the transfer coupling strength on the transferred particle and experimental Q-value distributions. Because of the availability of Q distributions measured at the two beam energies of 96 and 103 MeV, two sets of transfer coupling strength were determined for each transfer channel. The study with the upgraded code indicates transfers with negative ground-to-ground states Q value as the leading cause of the smearing of the barrier distribution. At the beam energy of 103 MeV, the smoothing of Dqe is influenced mainly by the one-neutron pickup. On the other hand, the one-neutron pickup and one-proton stripping transfers are dominant for the beam energy of 96 MeV. These results highlight the importance of the transfer coupling dependence on the experimental Q-value distribution and, consequently, on the dissipation of the projectile kinetic energy.