Photodesorption of SO2 in mixed ices under ultraviolet irradiation

Recent infrared spectroscopic observations have found high abundances of SO₂ in the interstellar medium, protoplanetary disks and comets. SO₂ ices have been previously characterised in the laboratory, although there is still much to learn about their interaction with other chemical species in mixed ices, including photodisorption yields and chemical products under irradiation. 

In this work we study photodisorption for mixed ices of SO₂ and CO under ultraviolet photon irradiation. Ice samples were grown by vapor deposition at 10 K in ultra high vacuum conditions. Irradiation source was a microwave-discharged hidrogen-flow lamp. Ices and their mixture ratios were identified using infrared absorption spectroscopy. Photodisorption was measured directly in the gas phase using quadrupole mass spectroscopy. 

We report photodisorption yields for SO₂ and CO for different mixture ratios, along with detailed spectroscopic study of the effects of mixture ratios on the shape and position of infrared absorption bands. Band strengths for the mixed ices are estimated experimentally, in relation to pure ices, as well as computationally using density functional theory.