The distribution of the intensity of scattering for angles ranging from 10 to 105 degrees has been experimentally determined for various solids. For paraffin and aluminum the scattering occurred at an effective wave-length for the primary rays of 0.23A; for copper and lead the wave-length was 0.19A. These wave-lengths were determined from absorption measurements in aluminum. The scattering from paraffin and aluminum was from thin plates by the transmission method, while that from copper and lead was from thick plates by reflection. The ratios of intensities at any given angles to those at 90 degrees were corrected for the different ionization effects at those angles, on account of the change of wave-length due to the Compton effect. Comparison of the experimental results for paraffin with the predictions of the Breit-Dirac theory of scattering from free electrons shows distinct excess scattering. This part of the work has been performed with a precision of about 1 percent. In addition, the $S$-values (scattering per electron) were computed for the various materials from their experimental scattering functions, using the paraffin value at 90 degrees, as predicted by the Dirac theory, as the basic measure. The $S$-values from aluminum have a most probable error of less than 2 percent, while those from copper and lead, being based upon a not entirely satisfactory computation, are assigned less than 6 percent. Curves have been plotted of the $S$-values against $\frac{\left[sin\right(\frac{\phi }{2}\left)\right]}{\lambda }$. The $S$-values show a large increase with the atomic number of the scatterer for the smaller values of $\frac{\left[sin\right(\frac{\phi }{2}\left)\right]}{\lambda }$, while for the larger values they tend to come together.

• Received 8 August 1932

DOI:https://doi.org/10.1103/PhysRev.42.153