Rotational Spectroscopy as a Tool for Structure-Specific Identification of Products of Uv-Photolyzed Cosmic Ice Analogues

Abstract

Cosmic ice analogue experiments are an important aspect of astrochemistry because they help researchers construct the chemical pathways leading to molecules found in young stellar objects, comets, and meteorites. Decades of cosmic ice experiments have demonstrated the formation of various organics and how ice composition is affected by UV photons and temperature. The ice chemistry can be challenging to elucidate, and structure-specific techniques are required to uniquely identify products. We present the Sublimation Laboratory Ice Millimeter/submillimeter Experiment (SubLIME), which uses rotational spectroscopy to complement previous laboratory ice studies. Using this technique, we can detect a wide range of products, including structural and conformational isomers, of UV-photolyzed ice samples from a single spectrum. Furthermore, this technique can be used to model the observational spectra of pre-and protostellar cores and cometary comae. We will present the SubLIME setup and new spectroscopic results of sublimated UV-photolyzed ice samples containing water (H 2 O) and carbon monoxide (CO).

Conformer Distributions of n-Propyl Cyanide in the Gas Phase and Following Ice Sublimation Measured by Broadband Rotational Spectroscopy

“…Indeed, these rigorous models and high-level calculations could be greatly improved with additional input from experimental measurements as to the isomer and conformer-specific energy ordering, rates of reactions, and product branching ratios associated with the chemistry occurring in and on icy grains. Although not inherently structure-specific, the study of ices using Fourier transform infrared spectroscopy (FTIR) and mass spectrometry (MS) has yielded profound insight into the chemistry of icy grains. − Additional techniques have recently emerged that offer isomer and conformer-specific probes of ice chemistry such as that reported by Theulé et al, Yocum et al, , and recently by our group . The former approaches employ radiation in the THz and mm-wave regimes, in a way analogous to detection by radiotelescopes, to study molecules that have desorbed from ices.…”

“…Although not inherently structure-specific, the study of ices using Fourier transform infrared spectroscopy (FTIR) and mass spectrometry (MS) has yielded profound insight into the chemistry of icy grains. 23−32 Additional techniques have recently emerged that offer isomer and conformer-specific probes of ice chemistry such as that reported by Theuléet al, 33 Yocum et al, 34,35 and recently by our group. 36 The former approaches employ radiation in the THz and mm-wave regimes, in a way analogous to detection by radiotelescopes, to study molecules that have desorbed from ices.…”