The azimuthal angular distribution of the photoprotons produced in the reaction ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}(\gamma , p_0){}_{}{}^{11}{}_{}{}^{}\mathrm{C}$ by monochromatic polarized gamma rays from ${}_{}{}^3{}_{}{}^{}\mathrm{T}(p, \gamma ){}_{}{}^4{}_{}{}^{}\mathrm{He}$ was measured for gamma-ray energies of 21.3 and 21.6 MeV. The ratio $R$ of the number of photoprotons with directions between 0° and 45° (with respect to the gamma-ray polarization) to the number between 45° and 90° was determined. The average observed ratio for $R$, 2.8±0.7, is larger than but not inconsistent with that calculated for pure electric-dipole photon absorption, 2.08±0.1.

• Received 20 April 1966

DOI:https://doi.org/10.1103/PhysRev.149.798