| Name: | Namrata Rani |
| Affiliation: | Universidad de Concepción, Chile |
| Conference ID: | ASI2025_263 |
| Title: | Formation of Thioacetaldehyde and Dithiol in the Interstellar Medium: Mechanisms and Binding Energy Analysis |
| Authors: | Namrata Rani 1, Stefan Vogt-Geisse 1, Stefano Bovino 2,3 |
| Authors Affiliation: | 1Departamento de Físico-Química, Facultad de Ciencias Químicas, Universidad de Concepción, Concepción, Chile
2 Dipartimento di Chimica, Sapienza, Università di Roma, Italy
3 Departamento de Astronomía, Facultad Ciencias Físicas y Matemáticas, Universidad de Concepción, Concepción, Chile |
| Mode of Presentation: | Oral |
| Abstract Category: | Stars, Interstellar Medium, and Astrochemistry in Milky Way |
| Abstract: | The chemistry behind sulfur depletion in cold, dense molecular clouds remains poorly understood, with a significant discrepancy between elemental sulfur abundance and detected molecular species in the interstellar medium (ISM). In this study, we explore the formation of thioacetaldehyde—the sulfur analogue of acetaldehyde—through both gas-phase reactions and surface-mediated processes on amorphous solid water (ASW) ice grains. Using high level quantum-chemical methods and the Binding Energy Evaluation Platform (BEEP), we identify favourable reaction sites on ASW, with thioethanol acting as a precursor.
Interestingly, our computations revealed an unplanned but thermodynamically more stable by-product, dithiol, alongside the formation of thioacetaldehyde. While thioacetaldehyde is favorable both kinetically and thermodynamically, the unexpected formation of ethane-di-thiol highlights the potential for multiple sulfur-containing species to coexist under ISM conditions. To predict where these molecules might reside, we conduct binding energy calculations to determine their distribution across different snowlines.
To gain deeper insights, we also compare the binding energies of thioacetaldehyde and precursor thioethanol with their oxygen analogues, such as acetaldehyde and ethanol. This comparison helps us understand the differences in adsorption behavior and chemical stability between oxygen- and sulfur-bearing molecules on dust grains. The binding energy data suggest that the molecular adsorption strength may vary across snowline regions, potentially leading to the segregation or co-location of sulfur and oxygen analogues on interstellar dust grains.
These findings contribute to the understanding of complex sulfur reservoirs in the ISM, proposing a new chemical network for sulfur-bearing organic molecules. Additionally, the potential future detection of both thioacetaldehyde and dithiol, much like acetaldehyde, would provide further evidence of sulfur's incorporation into complex molecular structures, bridging the gap between elemental sulfur and observed molecular forms in space.
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