Stimulated Raman scattering on rotational and vibrational transitions in nitrogen gas

Results are presented (thresholds of the effects and spectral characteristics) of an experimental investigation of rotational (RSTRS) and vibrational stimulated Raman scattering (VSTRS) in nitrogen at low pressures (1 < p < 5 atm) and of VSTRS at pressures up to 400 atm. The RSTRS threshold did not depend on pressure and was close to the theoretical estimates whilst the VSTRS threshold at p < 2.5 atm was influenced by the correlation between the Stokes and anti-Stokes components. The relative proportion of the anti-Stokes component at p = 2 atm was 1.5%. The RSTRS spectrum contained both lines of the spontaneous spectrum for J = 0–18 and the frequencies ν_L± 8 Bn. In the range of competition between these two effects (2 < p < 2.5 atm) this spectrum was converted into vibrational although the conditions for direct excitation of the rotational–vibrational bands were not satisfied.