Calculation method for many-level systems interacting with a resonant field of a high-power light wave

A theoretical analysis is made of the interaction of a quantum system characterized by two groups of closely spaced levels with a strong resonant field of a steady-state pump wave and a weak field of a "verifying signal." The strong field is allowed for by the canonical transformation and the weak field by the perturbation theory. The first-order susceptibilities are obtained for the weak field in the form which can be used to study the dependences of the frequencies, intensities, and widths of lines in the scatteredradiation spectrum on the frequency and intensity of the strong wave.