Rayleigh-Brillouin Scattering in Binary Gas Mixtures

TL;DR

This study investigates Rayleigh-Brillouin scattering in noble gas mixtures, revealing how a small helium admixture influences spectral lineshapes and confirming theoretical models without adjustable parameters.

Contribution

It provides the first detailed experimental analysis of spectral lineshapes in noble gas mixtures with helium and validates a parameter-free theoretical model.

Findings

He affects density fluctuation relaxation without contributing significantly to scattered light

Excellent agreement between experimental data and theory for mono-atomic gases

Results advance understanding of light scattering in complex molecular media

Abstract

Precise measurements are performed on spectral lineshapes of spontaneous Rayleigh-Brillouin scattering in mixtures of the noble gases Ar and Kr, with He. Admixture of a light He atomic fraction results in marked changes of the spectra, although in all experiments He is merely a spectator atom: it affects the relaxation of density fluctuations of the heavy constituent, but its contribution to the scattered light intensity is negligibly small. The results are compared to a theory for the spectral lineshape without adjustable parameters, yielding excellent agreement for the case of binary mono-atomic gases, signifying a step towards modeling and understanding of light scattering in more complex molecular media.