Inelastic Scattering of Gamma Rays by Bound Electrons

With incident $\gamma$ 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 $\gamma$ 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.