Stimulated Brillouin scattering from N2 and CH4 using a giant-pulse laser has been observed in an arrangement whereby the laser cannot relase and amplify the back-scattered radiation. This allows a quantitative study of the parameters affecting stimulated Brillouin scattering. The back-scattered beam converges at the same angle at which the laser beam diverges. The Brillouin component can have a narrow spectral width, one-third that of the laser itself, and in some cases can have a duration of only a few nanoseconds. N2 at high pressure can back-scatter as much as 45% of the incident power. The speeds of sound in CH4 and N2 have been measured at lower pressures than were previously reported.
T. A. Wiggins, R. V. Wick, and D. H. Rank, "Stimulated Effects in N2 and CH4 Gases," Appl. Opt. 5, 1069-1072 (1966)