Collision induced absorption in HITRAN2024: Enhanced and improved data for atmospheric and planetary studies

Abstract

Collision-Induced Absorption (CIA) phenomena play a key role in the atmospheric energy balance, making their accurate parametrization a decisive factor in modeling planetary atmospheres. This is the primary reason why the HITRAN spectroscopic database includes a dedicated section for CIAs. This section became available for the first time in 2012, followed by its first update in 2019. Six years since the first update, and with a significant amount of new data now available, it is timely to issue a second update. In this update, new data regarding collisional pairs that appear in the CIA section for the first time ( N₂–Ar, and CO₂– H₂O) are presented. Concerning collisional pairs already present in the database, new data extending both spectral and temperature ranges are available for CO₂– CO₂, CO₂– H₂, CO₂– CH₄, H₂– N₂, O₂– O₂, and O₂– CO₂, while new experimental data about H₂– H₂ and H₂–He have been included alongside the respective theoretical calculations. Data sources, comparisons among different data, and selection criteria, are discussed in detail. The final section is focused on identifying the CIA data that would be most valuable for the planetary science and astrophysics community in the future.