Scattering and absorption differential cross sections for double photon Compton scattering

The scattering and absorption differential cross sections for nonlinear QED process such as double photon Compton scattering have been measured as a f unction of independent final photon energy. The incident gamma photons are of 0.662 MeV in energy as produced by an 8 Ci (CS)-C-137 radioactive source and thin aluminum foils are used as scatterer. The two simultaneously emit ted photons in this process are detected in coincidence using two NaI(T1) s cintillation detectors and a slow-fast coincidence set-up of 30 nsec resolv ing time. The measured values of scattering and absorption differential cro ss sections agree with theory within experimental estimated error.