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.
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