Pressure Broadening Coefficients of N2O and SO2 for Studies of Exoplanetary Atmospheres

Kurzfassung

The new and upcoming generation of telescopes, including the ELT, ARIEL, GRAVITY+ and the JWST, significantly improves our ability to characterize exoplanetary atmospheres by producing data with higher spectral resolution and sensitivity. Interpreting these observations requires accurate spectroscopic modeling, which in return needs the knowledge of molecular parameters such as transition frequencies, line intensities, temperature and pressure broadening coefficients, among many others. However, to constrain these extensive theoretical models, laboratory measurements are needed. While large spectroscopic databases, such as HITRAN (Rothman et al., 2013) or ExoMol (Tennyson et al., 2024), provide extensive molecular line lists, the necessary parameters are not yet complete. In particular, pressure-broadening parameters of many molecules under conditions relevant to exoplanetary atmospheres are missing. N2O and SO2 are two such molecules with lacking pressure-broadening information. Both are considered (indirect) biosignatures due to their association with biological and geological activity (Seager et al., 2016; Schwieterman et al., 2018). While N2O has yet to be detected, SO2 was recently identified in exoplanetary atmospheres, e.g. in WASP39-b (Alderson et al., 2023; Rustamkulov et al., 2023). However, pressure-broadening information for both these molecules, particularly in He- and H2- dominated environments, remains limited. To address this, we present high-resolution gas-phase spectroscopy using the Bruker 120/5HR in the infrared to determine the pressure-broadening coefficients of N2O and SO2 at room temperature, up to about 1000 mbar. We focus on the effects of He, CO2, and H2 as broadeners, as these gases represent the dominating gases in diverse exoplanetary atmospheres. This talk focuses on the He-induced pressure-broadening coefficients, presenting new experimental data to improve our understanding of exoplanets.