THE REACTION HE-3(GAMMA,PP)N AT LOW NEUTRON RECOIL MOMENTUM

The reaction He-3(gamma,pp)n was measured at the ALS-Saclay at kinemat ics corresponding to mean neutron recoil momenta near 30 and 75 MeV. D ifferential cross sections were obtained for photon energies between E (gamma) = 200 and 450 MeV at proton emission angles relative to the p- p center of mass of 49-degrees and 75-degrees, and a proton angular di stribution was obtained at E(gamma)=350 MeV. The cross section for pho ton absorption by a p-p pair is found to be lower by two orders of mag nitude compared to that for a p-n pair in He-3. Theoretical multiple s cattering calculations reproduce the data rather well, except for sign ificant discrepancies at low E(gamma) and forward proton angles.