Inelastic Scattering of Gamma Rays by Bound Electrons

With incident γ rays of energy 662 keV the energy spectrum of the photons inelastically scattered by the K-shell electrons of lead has been studied, employing NaI(Tl) scintillation spectrometers and coincidence techniques. The energy spectrum of the γ rays scattered at 124^∘{} to the incident direction is observed to be a continuum from zero energy to about 570 keV. At 60^∘{} also the spectrum shows the same trend. The observed photon energy spectrum is found to differ to a very great extent from that calculated on the basis of the various nonrelativistic theories.The cross section for the inelastic scattering of the 662-keV γ rays by a K-shell electron of lead, at 124^∘{}, for scattered photon energy greater than 160 keV is estimated to be (1.78±{}0.16) times that by a free electron.