Rotational Spectroscopy as a Sublime Tool for Identifying Organic Products of UV-Photolyzed Cosmic Ice Analogues

A variety of organic compounds have been detected in comets, meteorites, and the cold gas enveloping young stellar objects. These compounds display a range of complexity and include complex organic molecules (COMs) that have astrobiological implications. Laboratory studies of energetically processed interstellar, planetary, and cometary ice analogues have demonstrated a large inventory of chemical formation routes and require sensitive analytical techniques to identify the composition of ice and gas products formed during processing. The unique identification of organics can be challenging and often requires structure-specific techniques to identify structural isomers, conformers, and isotopologues. We present the approaches used in the Sublimation of Laboratory Ices Millimeter/submillimeter Experiment (SubLIME), which uses the structure-specificity of rotational spectroscopy to identify the composition and abundance ratios of sublimated products of UV-photolyzed ice samples. Ice samples are photolyzed at low temperature (~10 K) and slowly heated to 300 K to sublimate the volatile products. The sublimated gas mixture is then analyzed with millimeter/submillimeter spectroscopy, and the resulting spectra can be directly compared to observational spectra collected with submillimeter/far-IR telescopes. We will present the experimental set-up and new results of UV-photolyzed interstellar ice analogues containing water (H₂O), carbon monoxide (CO), and methanol (CH₃OH). Formation routes for identified COMs will be proposed for follow-up experimental and theoretical investigations.