Laboratory Rotational Spectroscopy Leads to the First Interstellar Detection of Singly Deuterated Methyl Mercaptan (CH2DSH)

Laboratory Rotational Spectroscopy Leads to the First Interstellar Detection of Singly Deuterated Methyl Mercaptan (CH2DSH)

We report an extensive rotational spectroscopic analysis of singly deuterated methyl mercaptan (CH _2 DSH) using both millimeter and far-infrared synchrotron spectra to achieve a global torsional analysis of the three lowest torsional substates ( e _0 , e _1 , and o _1 ) of this nonrigid species. A...

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Main Authors: Hayley A. Bunn, Silvia Spezzano, Laurent H. Coudert, Jean-Claude Guillemin, Yuxin Lin, Christian P. Endres, Brant Billinghurst, Olivier Pirali, Jes Jørgensen, Valerio Lattanzi, Paola Caselli
Format: Article
Language:English
Published: IOP Publishing 2025-01-01
Series:The Astrophysical Journal Letters
Subjects:
Astrochemistry
Laboratory astrophysics
Molecular spectroscopy
Interstellar molecules
Interstellar abundances
Online Access:https://doi.org/10.3847/2041-8213/adacea
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Summary:We report an extensive rotational spectroscopic analysis of singly deuterated methyl mercaptan (CH _2 DSH) using both millimeter and far-infrared synchrotron spectra to achieve a global torsional analysis of the three lowest torsional substates ( e _0 , e _1 , and o _1 ) of this nonrigid species. A fit including 3419 millimeter-wave transitions along with 43 infrared torsional subband centers was performed with rms deviations of 0.233 MHz and 0.270 cm ^−1 , respectively, resulting in 68 fit parameters. A spectroscopic catalog built from this analysis for a temperature of 125 K has led to the first interstellar detection of CH _2 DSH toward the solar-like protostar IRAS 16293-2422 B. We report the identification of 46 transitions, including eight relatively unblended lines, resulting in a derived column density of (3.0 ± 0.3) × 10 ^14 cm ^−2 . The column density ratio for HDCS/CH _2 DSH compared to HDCO/CH _2 DOH suggests a difference in the interstellar chemistry between the sulfur and oxygen complex organics, in particular a different link between H _2 CO and CH _3 OH and between H _2 CS and CH _3 SH. This is the first interstellar detection of a deuterated sulfur-bearing complex organic molecule and therefore an important step toward understanding the chemical origin of sulfur-based prebiotics.
ISSN:2041-8205

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