Study of the Brillouin linewidth in gas mixtures

Abstract

In this paper, a theoretical method is presented to calculate Brillouin linewidth (BLW) in gas mixtures. The presented model is based on Newton's viscosity law and the kinetic theory of gases. From a combination of Chapman–Enskog theory and Navier–Stokes mathematical model, we recovered the appropriate terms of the viscosity tensor for gas mixtures. We demonstrated that viscosity is not necessarily the dominant mechanism in the enhancement or suppression of the BLW in a gas mixture, and other parameters, such as density, can be dominant instead. It was found that the contribution of thermodynamics quantities was negligible compared to other parameters. The numerical results were also compared to those obtained from the molar refraction-mixing method and confirmed that these results were completely coherent.