Reaction mechanism of (α,d) transfer in Pb208(α,d)Bi210 at 33 and 48 MeV

The reaction Pb208(α,d)Bi210 has been studied at 33 and 48 MeV with particular emphasis on the (h92g92) ground-state multiplet and the high-spin members of other low-lying n-p multiplets, which are expected to be of high purity. About 50 angular distributions were obtained and used as a basis for a study of the transfer mechanism in (α,d) reactions. The analysis was made with the microscopic distorted-wave Born approximation and with two-step coupled-reaction-channel calculations. The L transfers observed ranged from L=1 to L=13 and were consistent with one-step transfer selection rules. Nevertheless, the relative magnitudes of cross sections to levels of the (h92g92) ground-state multiplet disagree with one-step-transfer predictions at either beam energy by factors which vary from 0.5 to 4.0. This phenomenon is explained as a coherent addition of the sequential stripping amplitudes (α,t;t,d) and (α,He3;He3,d) to the one-step amplitude, where the important (α,t;t,d) amplitude typically amounts to about 50% of the one-step (α,d) amplitude for high- and low-spin states alike. Details of the coupled-reaction-channel analysis are provided. The two-step calculations were kept free of arbitrary parameters by a simultaneous analysis of previously published Pb208(t,d), Pb208(He3,d), Pb208(α,t), and Pb208(α,He3) single-particle transfer data. This systematic reanalysis indicated again that most single-particle states in Pb209 and Bi209 show their full spectroscopic strength, but that the πi132 and νj152 single-particle states are not pure and have single-nucleon spectroscopic factors of about 0.75±0.10. NUCLEAR REACTIONS Pb208(α,d)Bi210, Eα=33 and48 MeV, measured Ed and σ(θ,Ed) with QDDD spectrograph. DWBA and CRC analysis, deduced levels, Lα,d, evidence for sequential stripping.