S-MATRIX FORMULATION OF THE CHARGED-PARTICLE SCATTERING IN THE PRESENCE OF A LASER-RADIATION FIELD .2. LOW-FREQUENCY APPROXIMATION

A low-frequency approximation to the previously derived Born series for charged-particle elastic scattering in the presence of a laser radiation field is presented. The approximation procedure is based upon the condition that the transition frequency from the initial to the intermediate free states be much greater than the field frequency. The resulting elastic-scattering Born series with the field has the same analytic structure as the corresponding field-free Born series, but with free-particle energies and momenta duly renormalized to incorporate the effect of the field. As part of the results presented here has been obtained also by Kroll and Watson in a different treatment, the present approach is additionally meant to provide a detailed alternative derivation of these results. © 1979 Società Italiana di Fisica.