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Cross sections for the elastic scattering of 88.03-keV For gold, 7.3 keV above its threshold, the experiment agrees with the S-matrix prediction. However, for lead some 25 eV above threshold, the experimental value is about 40% larger than predicted, while for bismuth (2.5 keV below threshold), experiment lies 70% above theory. The measured K-shell photoeff'ect cross section of lead is within 10%%uo of the prediction based on the independent-particle approximation.

Cross sections for the elastic scattering of 88.03-keV For gold, 7.3 keV above its threshold, the experiment agrees with the S-matrix prediction. However, for lead some 25 eV above threshold, the experimental value is about 40% larger than predicted, while for bismuth (2.5 keV below threshold), experiment lies 70% above theory. The measured K-shell photoeff'ect cross section of lead is within 10%%uo of the prediction based on the independent-particle approximation.

Compton scattering of 320-keV y 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 quasiCompton regime. The single-differential cross sections obtained after a correction for bremsstrahlung are in reasonable agreement with theoretical calculations.

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