We show in this note that, in the coherent Rayleigh-Brillouin scattering (CRBS) experiment [X. Pan, M. N. Shneider, and R. B. Miles, Phys. Rev. A 69, 033814 (2004)], the vibrational modes of the $\mathrm{C}{\mathrm{O}}_2$ molecules are frozen. When the gas dynamic parameters are chosen accordingly, the model predicts a line shape that matches with the experimental data. Fitting the theoretical curve to the CRBS data represents a method to measure the speed of high-frequency sound, bulk viscosity, and the rotational relaxation time of molecular gases.

• Received 18 June 2004

DOI:https://doi.org/10.1103/PhysRevA.71.045801