Work

First-principles calculations of far-wing absorption in He-broadened CO 2 infrared spectra

Year: 2026

Type: article

Abstract: We report theoretical predictions and modeling of the far-wing absorption of CO 2 broadened by He over a wide temperature range (200–1000 K), which are relevant for exoplanet atmosphere studies. Accurate modeling of He-broadened CO 2 absorption is essential for opacity calculations used to characterize the composition, structure, and climate of exoplanet atmospheres. In particular, the strong CO 2 band at 4.3 µm has been clearly identified in the spectra of several exoplanets observed with the James Webb Space Telescope (JWST). Requantized classical molecular dynamics simulations were first performed to predict absorption in the far wings of the 4.3 µm band of CO 2 . The resulting predictions show excellent agreement with available experimental data at room temperature. The theoretical predictions and measured data were then used to parameterize an impact energy-corrected sudden model, which allowed us to accurately reproduce the far-wing absorption of He-broadened CO 2 in several infrared spectral regions over the 200–1000 K temperature range. Finally, for applications to exoplanet atmosphere opacity calculations, we derived temperature-dependent χ -factor corrections that account for the sub-Lorentzian behavior of the far wing of the major infrared bands of CO 2 .

Source: Astronomy and Astrophysics

DOI: 10.1051/0004-6361/202662323

Authors: Ha Tran, Emile Ducreux