Fig. 5: Selected infrared peak profiles during the irradiation phase.

Each peak was tracked during the low (left), medium (center), and high (right) dose SO₂/CH₄ experiments. Methane (CH₄), sulfur dioxide (SO₂), ethane (C₂H₅), sulfur trioxide (SO₃), ν(S=O), and the methyl radical (CH₃^•) were tracked by the 1300 cm⁻¹, 1330 cm⁻¹, 2976 cm⁻¹, 1380 cm⁻¹, 1200 cm⁻¹, and 3160 cm⁻¹ peaks, respectively, along with their respective kinetic fits (red). The functional fits can be found in Supplementary Table 14. Error bars are calculated from instrumental noise and error in ice thickness measurements.