The problem of accounting for the anomalous scattering of gamma-rays suggests the importance of investigating the probability of processes in which an incoming quantum produces an electron-positron pair in the field of a nucleus, going on in a new direction with diminished energy. To determine the cross section in the general case is difficult, but an estimate of the total magnitude of the effect in the energy range of interest is obtained by a calculation of the cross section as a function of the energies of the incident and scattered quanta and the angle between them in the limit where the electron-positron pair is produced with small kinetic energy.

While there exists a possibility of observing the process under suitable experimental conditions, the cross section is found to be too small to contribute appreciably to the production of the hard component in the radiation from heavy elements exposed to penetrating gamma-rays.

• Received 12 June 1935

DOI:https://doi.org/10.1103/PhysRev.48.302