Pressure Broadening Coefficients of SO2 by He for Studies of Exoplanetary Atmospheres

Kurzfassung

The new and upcoming generation of telescopes, including the Extremely Large Telescope (ELT), ARIEL, GRAVITY+, and the James Webb Space Telescope (JWST), is significantly expanding our ability to study exoplanetary atmospheres thanks to higher spectral resolution and sensitivity. To interpret the resulting data, accurate spectroscopic modeling is essential. This, in turn, requires detailed knowledge of molecular line parameters such as transition frequencies, line intensities, temperature and pressure broadening coefficients, among others. Laboratory measurements play a crucial role in providing these data. The spectroscopic parameters needed for the modeling are typically stored in large spectroscopic databases, such as HITRAN (Rothman et al., 2013) or ExoMol (Tennyson et al., 2024). While these databases offer extensive molecular line lists, they remain incomplete, especially regarding pressure-broadening parameters for conditions relevant to exoplanetary atmospheres. One molecule for which this is particularly true is sulfur dioxide (SO2), which is considered a potential indirect biosignature due to its association with biological and geological activity (Seager et al., 2016; Schwieterman et al., 2018). With its recent detection in the exoplanetary atmosphere of the hot Saturn WASP-39b (Alderson et al., 2023; Rustamkulov et al., 2023), it is the first molecule linked to photochemistry. Since the atmosphere of gas giants is primarily composed of H2 and He, understanding how these gases affect SO2's spectral line shape at high pressure is essential. We conduct high-resolution gas-phase spectroscopy to address this gap using the Bruker 120/5HR FTIR in the infrared spectral region. We aim to determine the pressure-broadening coefficients of SO2 at room temperature for pressures up to approximately 1000 mbar. We will examine the effects of He, CO2 and H2 as collision partners, representing the dominating gases in exoplanetary atmospheres. With this poster, we present new experimental results for He-induced broadening of SO2, offering essential data to improve our understanding of exoplanets such as WASP-39b.