Two-proton pickup studies with the (6Li,8B) reaction

The (6Li, 8B) reaction was investigated on targets of 26Mg, 24Mg, 16O, 13C, 12C, 11B, 10B, and 9Be at a bombarding energy of 80.0 MeV, and on targets of 16O, 12C, 9Be, 7Li, and 6Li at a bombarding energy of 93.3 MeV. Only levels consistent with a direct, single-step two-proton pickup reaction mechanism were observed to be strongly populated. On T/sub z/ = 0 targets, the spectroscopic selectivity of this reaction resembles that of the analogous (p,t) reaction. Additionally, these data demonstrate the dominance of spatially symmetric transfer of the two protons. On T/sub z/ > 0 targets the (6Li, 8B) reaction was employed to locate two previously unreported levels (at 7.47 +- 0.05 MeV and 8.86 +- 0.07 MeV) in the T/sub z/ = 2 nuclide 24Ne and to establish the low-lying 1p-shell states in the T/sub z/ = 3/2 nuclei 11Be, 9Li, and 7He. However, no evidence was seen for any narrow levels in the T/sub z/ = 3/2 nuclide 5H nor for any narrow excited states in 7He. The angular distributions reported here are rather featureless and decrease monotonically with increasing angle. This behavior can be shown by a semi-classical reaction theory to be a consequence of the reaction kinematics. A semiclassical approach also suggests that the kinematic term in the transition matrix element is only weakly dependent upon the angular momentum transfer (which is consistent with simple distorted wave born approximation calculations). However, only qualitative agreement was obtained between the observed relative transition yields and semiclassical predictions, using the two-nucleon coefficients of fractional parentage of Cohen and Kurath, probably due to the limitations of the semi-classical reaction theory