Compton scattering of 320-keV γ rays byK-shell electrons of holmium and gold

Compton scattering of 320-keV {γ} rays through 45^∘{} and 115^∘{} by K-shell electrons of gold and holmium has been studied by the well-known coincidence technique. Double-differential cross sections with respect to outgoing photon energy and angle have been determined from 30 keV up to the kinematic limits. Target-Z-dependent false coincidences arising from bremsstrahlung emitted by photoelectrons were estimated both by theoretical analysis and by measurements carried out with gold targets of thicknesses differing by more than a factor of 4. The analysis of the bremsstrahlung process included the often neglected effects of the angular distribution of photoelectrons and of multiple scattering of electrons during the slowing-down process within the target. The bremsstrahlung generated false coincidences obscure the possible observation of the predicted infrared divergence in the low outgoing photon energy regime and lead to a significant contribution even in the quasi-Compton regime. The single-differential cross sections obtained after a correction for bremsstrahlung are in reasonable agreement with theoretical calculations.