12C(d, pγ) 13C angular distributions and correlations near threshold

Abstract

Proton-gamma angular correlations from the 12C(d, pγ) 13C on through the 3.68 and 3.85 MeV states of 13C have been measured at bombarding energies from 2 to 3 MeV and at a strong E d = 2.50 MeV resonance. Yield curves and proton angular distributions for these groups and for protons leaving 13C in the 3.09 MeV state have also been measured. These reactions satisfy the condition E d ≃ −2 Q for which distortions of plane wave stripping theory might be expected to be small. The correlation anisotropies are maximum and the symmetry axis shifts and azimuthal anisotropies are almost zero both at the minimum bombarding energy and at the 2.50 MeV resonance. Highly distorted correlations and distributions are seen at only 2.62 MeV. The 12C(d, p) 13C 3.85 angular correlation at E d = 2.50 MeV involves single-particle resonances both in 14N and in 13C and is an interesting example of a resonant direct reaction. The reduced widths derived from plane wave stripping theory are too low by factors of 3 to 10 and are energy dependent. Thus, while distortions clearly affect reduced widths, the detailed angular properties of the reactions are very closed to the predictions of plane wave theory.