Elastic and inelastic scattering of 50-MeV α particles by 6Li and 7Li nuclei: The role of exchange effects in anomalous scattering at large angles

Elastic and inelastic scattering of 50.5-MeV α particles with the excitation of the Jπ=3+(Ex=2.185 MeV) state of 6Li and the Jπ=1/2- (Ex=0.478 MeV) and Jπ=7/2-(Ex=4.63 MeV) states of 7Li are studied in the angular range 10 deg. -170 deg. in the laboratory frame. The measured angular distributions are analyzed in the optical model and in the DWBA. It is shown that the experimental angular distributions can be described in the full angular range only if the exchange mechanism of elastic and inelastic transfer of the deuteron and triton clusters is taken into account. Cluster spectroscopic factors extracted for the ground states of 6Li and 7Li nuclei (Sαd=1.39±0.15 and Sαt=1.03±0.1) from the comparison of theoretical results with experimental data on large-angle scattering agree well with theoretical predictions and data known from quasielastic knockout reactions. For excited states, the values of the experimental d and t spectroscopic factors are almost one-third as large as the above values for the ground states