The E2/M1 amplitude ratio in a dc-field-induced two-laser-wave mixing in atoms

The effect of a dc electric and (or) magnetic field on the cross section for coherent mixing of two laser waves in atoms is determined. Analytic expressions are obtained for the cross-section dependence on polarisation of incident and generated waves, which allow the measurement of the E2/M1 amplitude ratio Q from the efficiency of a constant-field-induced coherent process for collinear waves. Analytic expressions are also derived for the polarisation dependence of the cross section for frequency mixing in indium and thallium atoms.