Determination of Rayleigh scattering cross sections and indices of refraction for Ar, CO2, SF6, and CH4 using BBCES in the ultraviolet

Rayleigh scattering cross sections for argon, carbon dioxide, sulfur hexafluoride, and methane were measured using Broadband Cavity Enhanced Spectroscopy (BBCES) between 264 and 297 nm, extending the region of experimental cross section data available for all four gases. The experimentally derived values for Ar and CO2 are in excellent agreement with refractive index based (n-based) calculations, within 0.8% and 1.0% on average, respectively. Our measured Rayleigh scattering cross sections for SF6 and CH4, however, suggest that n-based calculations for these gases should be revised. We derive new dispersion relations for SF6 and CH4, incorporating data from this study and from our previous work at 333-363 nm, to provide improved indices of refraction and n-based Rayleigh scattering cross sections. (c) 2020 Elsevier Ltd. All rights reserved.