Elastic scattering cross-sections of lead, tantalum and molybdenum were determined with the help of a Ge (Li) detector for 1.17 and 1.33 MeV rays between 30° and 115°. Theoretical evaluations of the cross-sections are based on a coherent addition of the well-known nuclear Thomson scattering amplitudes, the Rayleigh amplitudes calculated by Kissel and Pratt and the Delbrück amplitudes given by Papatzacos and Mork. The fairly good agreement between experiment and theory reveals the importance of the real Delbrück amplitudes. However, the experimental results in the 30–60° range tend to lie slightly but systematically below the calculated cross-sections.

A recently reported study [Phys. Rev.A49, 3664 (1994)] of elastic scattering of 81 keVγ rays in the angular range from 60° to 133° has been extended to smaller and larger angles. Previously reportedS matrix calculations of atomic Rayleigh scattering have been shown to require a subtraction of contributions from spurious resonances. Most of the experimental data are in agreement with the calculations. Calculations (MF + ASF) based on a combination of relativistic modified form factors (MF’s) and angle independent anomalous scattering factors (ASF’s) are found to be inadequate for an explanation of experimental cross-sections in the case of highZ elements at angles larger than about 120°.