THEORY OF SPECTRA OF COHERENT 4-PHOTON SCATTERING WITH 1-PHOTON RESONANCES DUE TO EXCITED AND AUTOIONIZING ATOMIC STATES

Coherent four-photon scattering of light due to excited and autoionizi ng states of atomic systems is considered. We analyze the influence of one-photon resonances at the frequency of the anti-Stokes signal and at the frequency of the pump wave on the shape of the spectrum of four -photon scattering. We derive analytical expressions for the line shap es of four-photon scattering involving one-photon resonances with allo wance for phase-matching conditions and variation in the populations o f excited states for limiting regimes of tight focusing and strong abs orption in a medium with cubic nonlinearity. The calculated spectra of four-photon scattering include the interference of resonant and nonre sonant components of third-order nonlinear susceptibility with allowan ce for one-photon saturation. We develop a method for normalizing expe rimental spectra of four-photon scattering with one-photon resonances that takes into account distortion of spectral lines due to the influe nce of phase mismatch and one-photon absorption.