(γ,2N) reaction in ¹²C

The ¹²C(γ,pn) and ¹²C(γ,pp) reactions have been measured for photon energies between 80 and 157 MeV using a photon tagging spectrometer and plastic scintillator detectors. The overall energy resolution was ∼7 MeV, sufficient to determine the initial shells of the emitted nucleons. Corrections were made for solid angle and threshold effects by means of Monte Carlo simulations. For the (γ,pn) reaction both the missing energy and recoil momentum distributions are largely consistent with a two-nucleon absorption process on p-shell an sp nucleon pairs. For the much smaller ¹²C(γ,pp) cross section the reaction mechanism is not yet understood but the recoil momentum distributions suggest that final state interactions are not dominant.