Quasielastic Processes in the Silicon + Lead Systems at 5--8 Mev/nucleon.

Quasielastic yields have been measured for the ^{28}Si + ^ {208}Pb reaction at E_ {rm lab}(^{28 }Si) = 152, 166, and 255 MeV, and for the ^{30}Si + ^ {208}Pb, ^{28} Si + ^{206}Pb, and ^{30}Si + ^{206}Pb reactions at E _{rm lab}(Si) = 222 MeV. Coupled -channels analysis of the elastic and inelastic scattering has been performed, resulting in the determination of an optical-model potential which describes the data over the range of energies and for different isotopes of Si and Pb. Excellent fits to the data were produced, with one notable exception. An inability to reproduce the angular distribution associated with the inelastic excitation of the 3^{-} state in ^{208}Pb was observed in the coupled -channels analysis of ^{28}Si + ^{208}Pb at 152 and 166 MeV, in spite of the excellent results obtained at 225 MeV. The hypothesis that this discrepancy reflects a strong coupling of the 3^{-} state to the neutron transfer channels was unable to be confirmed by coupled-channels calculations into which the one-neutron transfer channel had been approximately included. Measurements of the static quadrupole moments of the 2.2355 MeV and 3.4978 MeV 2^{+ } states of ^{30} Si have been made using the nuclear reorientation effects in the excitation of ^{30} Si by ^{208}Pb, giving Q_{2_sp{1} {+}} = -9(4) e fm ^{2} and Q_ {2_sp{2}{+}} = -4(9) e fm^2. The sign of the interference term for the transition between these two states is unambiguously determined to be negative (destructive). The total quasielastic transfer yields were observed to scale inversely with bombarding energy, saturating 38% of the total reaction cross section at the lowest energy and 25% at the highest energy. The one-neutron pickup yields comprised the largest single contribution. These transfer processes displayed a strong dependence on the ground state Q value. Together with other previously published single nucleon transfer cross sections, they were compared with the predictions from a Q -window model. This model was found to reproduce the measured yields extremely well. The one-nucleon transfer data were also analyzed using the distorted-wave Born approximation (DWBA) with optical-model parameters deduced from the coupled -channels analysis and spectroscopic factors taken from the literature. The agreement was found to be generally good.