Scattering and absorption cross sections of atmospheric gases in the ultraviolet–visible wavelength range (307–725 nm)

• Main Authors: Q. He, Z. Fang, O. Shoshanim, S. S. Brown, Y. Rudich
• Format: Article
• Language: English
• Published: Copernicus Publications 2021-10-01
• Series: Atmospheric Chemistry and Physics
• Online Access: https://acp.copernicus.org/articles/21/14927/2021/acp-21-14927-2021.pdf

<p>Accurate Rayleigh scattering and absorption cross sections of atmospheric gases are essential for understanding the propagation of electromagnetic radiation in planetary atmospheres. Accurate extinction cross sections are also essential for calibrating high-finesse optical cavities and differential optical absorption spectroscopy and for accurate remote sensing. In this study, we measured the scattering and absorption cross sections of carbon dioxide, nitrous oxide, sulfur hexafluoride, oxygen, and methane in the continuous wavelength range of 307–725 nm using broadband cavity-enhanced spectroscopy (BBCES). The experimentally derived Rayleigh scattering cross sections for CO<span class="inline-formula">₂</span>, N<span class="inline-formula">₂</span>O, SF<span class="inline-formula">₆</span>, O<span class="inline-formula">₂</span>, and CH<span class="inline-formula">₄</span> agree with refractive index-based calculations, with a difference of (0.4 <span class="inline-formula">±</span> 1.2) %, (<span class="inline-formula">−</span>0.6 <span class="inline-formula">±</span> 1.1) %, (0.9 <span class="inline-formula">±</span> 1.4) %, (2.8 <span class="inline-formula">±</span> 1.2) %, and (0.9 <span class="inline-formula">±</span> 2.2) %, respectively. The O<span class="inline-formula">₂</span>–O<span class="inline-formula">₂</span> collision-induced absorption and absorption by methane are obtained with high precision at the 0.8 nm resolution of our BBCES instrument in the 307–725 nm wavelength range. New dispersion relations for N<span class="inline-formula">₂</span>O, SF<span class="inline-formula">₆</span>, and CH<span class="inline-formula">₄</span> were derived using data in the UV–vis wavelength range. This study provides dispersion relations for refractive indices, <span class="inline-formula"><i>n</i></span>-based Rayleigh scattering cross sections, and absorption cross sections based on more continuous and more extended wavelength ranges than available in the current literature.</p>