Measurements and calculations of H2O broadened by CO2 collisional parameters for planetary atmospheres

Abstract

Collisional parameters of H₂O with CO₂ are currently missing from international spectroscopic databases, although they are essential for accurate modeling of water vapor in CO₂-rich planetary atmospheres. In this study, high-resolution infrared spectra of H₂O broadened by CO₂ were recorded using a Fourier Transform Spectrometer in the 1.18 and 2.34 µm spectral regions. CO₂-collisional parameters for selected H₂O transitions were derived through a multispectrum fitting procedure employing both Voigt and quadratic speed-dependent Voigt profiles. Furthermore, calculations based on the semi-classical Complex Robert-Bonamy-Ma formalism were performed to estimate CO₂-broadened half-widths, line shifts, and their temperature dependencies across various atmospheric transparency windows. It results in a strong agreement between theoretical predictions and experimental data. Finally, the shared calculated linelist, obtained for a wide range of transitions, can be directly applied to radiative transfer modeling of atmospheres primarily composed of carbon dioxide.