High-resolution Brillouin spectra were recorded for light scattered at small angles from liquid CS<sub>2</sub>. The use of a single-mode He-Ne laser, locked in frequency to a Fabry-Perot interferometer, permitted measurements of line widths of the order of 10 MHz for frequencies in the range 300–1000 MHz. These measurements extend previous Brillouin line-width measurements at higher frequencies into the region where relaxation effects are dominant and connect the optical measurements with lower-frequency acoustical data.
Robert W. Coakley and Robert W. Detenbeck, "Brillouin-scattering measurements of the acoustic absorption coefficient in liquid CS2," J. Opt. Soc. Am. 65, 6-9 (1975)