Rayleigh scattering cross sections of argon, carbon dioxide, sulfur hexafluoride, and methane in the UV-A region using Broadband Cavity Enhanced Spectroscopy

•Rayleigh scattering cross sections measured for gases from 333 to 363 nm with BBCES.•Results for Ar and CO2 in excellent agreement with refractive index based values.•Measurements for SF6 are lower than n-based by 2.2% but are within 2-σ uncertainty.•Measured CH4 cross sections are much lower (22%) than most recent n-based values.•New dispersion formula for CH4 reported in UV-A region with <2% uncertainty.