Investigation of the stimulated threephoton scattering at the excitation near resonant transition in rubidium atom

The spectral distribution and the intensity of induced three-photon scattering near the 5$^2$S$_{1/2}$—5$^2$P$_{1/2,3/2}$ resonance transitions of the rubidium atom upon excitation of a narrow (0.2cm$^{-1}$) frequency-tuned pumping line with intensities up to 30 MW/cm$^2$. The forced three-photon scattering was observed in the form of a wide asymmetric line. A much slower intensity falloff was always observed from the edge of the line, removed from resonance ω$_{0}$ frequency of the atomic transition. The highest-energy pulse due to induced three-photon scattering was attained upon long-wave divergence between pumping frequency ω$_{L}$ and the resonance frequency, i.e., ω$_{0}$-ω$_{L}$~1-4cm $_{-1}$. The dependence of the shift of the maximum of the line of induced three-photon scattering on ω$_{0}$-ω$_{L}$. It is shown that the location of the maximum and the intensity distribution of the induced three-photon scattering line are in satisfactory agreement with theoretical estimates, making allowance for the shift of atomic levels as a result of Stark's dynamic effect.