On the effect of long-wavelength electron plasma waves on large-angle stimulated Raman scattering of short laser pulse in plasmas

Spectral features of a large-angle stimulated Raman scattering (LA SRS) of a short electromagnetic pulse in an underdense plasma, which are caused by the presence in a plasma of a given linear long-wavelength electron plasma wave (LW EPW), are investigated. It is shown that the LW EPW, whose phase v elocity coincides with a group velocity of a pulse and a density perturbati on normalized to a background electron density deltan(LW)/n(0) exceeds the ratio of the electron plasma frequency to the laser frequency omega (pe)/om ega (0), suppresses the well-known Stokes branch of the weakly coupled LA S RS, Under the same condition, the anti-Stokes band appears in the spectrum of the scattered radiation, Variation of a scattering angle and an electron temperature do not significantly modify qualitative features of the effect . In the case of strongly coupled LA SRS, the maximum of the increment is d ecreased by nearly one-half for deltan(LW)/n(0) similar to (a(0)omega pe/om ega (0))(2/3) much greater than omega (pe)/omega (0), where a(0) is an ampl itude of an electron quiver velocity in the laser field normalized to a spe ed of light c, and it decreases further with an increase in plasma density perturbation in LW EPW.