Real and Virtual Radiation in Electron-Nucleus Scattering

Expressions are developed for the virtual photon spectrum and for the bremsstrahlung cross section, using the distorted-wave method for relativistic electrons in a Coulomb field. Evaluation of the matrix elements is made in terms of generalized hypergeometric functions, and some numerical results are given for electrons of energy 10 and 100 MeV. Significant enhancement of the virtual radiation spectrum is found to result from the use of distorted waves as opposed to plane waves. Calculations of the contributions of $E1$, $M1$, $E2$, and $E3$ radiation to the bremsstrahlung cross section, $\frac{{d}^{2}\ensuremath{\sigma}}{d\ensuremath{\omega}d\ensuremath{\Omega}}$, are also made; enhancement, similar to that observed with the virtual spectrum, is found in this case also.