Dataset Information

Rotational spectroscopic study of S-methyl thioformate: A global laboratory analysis of ground and excited torsional states up to 660 GHz.

ABSTRACT:

Context

S-methyl thioformate CH₃SC(O)H is a monosulfur derivative of methyl formate, a relatively abundant component of the interstellar medium (ISM). S-methyl thioformate being, thermodynamically, the most stable isomer, it can be reasonably proposed for detection in the ISM.

Aims

This work aims to experimentally study and theoretically analyze the ground and first torsional excited states for CH₃SC(O)H in a large spectral range for astrophysical use.

Methods

S-methyl thioformate was synthesized as a result of a reaction of methyl mercaptan with acetic-formic anhydride. The millimeter-wave spectrum was then recorded for the first time from 150 to 660 GHz with the solid-state spectrometer located at Lille.

Results

A set of 3545 lines is determined and combined with 54 previously measured lines in the microwave region, belonging to ground state ? _t = 0 as well as 1391 transitions in the first excited state of torsion ? ₁₈ = 1. Some 164 lines were also assigned to ? ₁₈ = 2 for the A-species. A global fit was performed using the BELGI-C_s code taking into account the large splitting of A and E lines due to methyl internal rotation motion with a relatively low barrier, V₃ = 127.4846(15) cm^-1.

Conclusions

Using our spectroscopy work, a deep search of S-methyl thioformate was carried out in the IRAM 30m and ALMA data of different high-mass star-forming regions (Orion KL and Sgr B2). We derived an upper limit to the CH₃SC(O)H column density in these regions.

SUBMITTER: Jabri A

PROVIDER: S-EPMC7116753 | biostudies-literature | 2020 Dec

REPOSITORIES: biostudies-literature

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Publications

Rotational spectroscopic study of S-methyl thioformate: A global laboratory analysis of ground and excited torsional states up to 660 GHz.

Jabri A A Tercero B B Margulès L L Motiyenko R A RA Alekseev E A EA Kleiner I I Cernicharo J J Guillemin J-C JC

Astronomy and astrophysics 20201207

<h4>Context</h4>S-methyl thioformate CH<sub>3</sub>SC(O)H is a monosulfur derivative of methyl formate, a relatively abundant component of the interstellar medium (ISM). S-methyl thioformate being, thermodynamically, the most stable isomer, it can be reasonably proposed for detection in the ISM.<h4>Aims</h4>This work aims to experimentally study and theoretically analyze the ground and first torsional excited states for CH<sub>3</sub>SC(O)H in a large spectral range for astrophysical use.<h4>Met ...[more]

PMID: 33594292

Similar Datasets

Project description:For all the amides detected in the interstellar medium (ISM), the corresponding nitriles or isonitriles have also been detected in the ISM, some of which have relatively high abundances. Among the abundant nitriles for which the corresponding amide has not yet been detected is cyanoacetylene (HCCCN), whose amide counterpart is propiolamide (HCCC(O)NH2). With the aim of supporting searches for this amide in the ISM, we provide a complete rotational study of propiolamide from 6 GHz to 440 GHz. Time-domain Fourier transform microwave (FTMW) spectroscopy under supersonic expansion conditions between 6 GHz and 18 GHz was used to accurately measure and analyze ground-state rotational transitions with resolved hyperfine structure arising from nuclear quadrupole coupling interactions of the 14N nucleus. We combined this technique with the frequency-domain room-temperature millimeter wave and submillimeter wave spectroscopies from 75 GHz to 440 GHz in order to record and assign the rotational spectra in the ground state and in the low-lying excited vibrational states. We used the ReMoCA spectral line survey performed with the Atacama Large Millimeter/submillimeter Array toward the star-forming region Sgr B2(N) to search for propiolamide. We identified and measured more than 5500 distinct frequency lines of propiolamide in the laboratory. These lines were fitted using an effective semi-rigid rotor Hamiltonian with nuclear quadrupole coupling interactions taken into consideration. We obtained accurate sets of spectroscopic parameters for the ground state and the three low-lying excited vibrational states. We report the nondetection of propiolamide toward the hot cores Sgr B2(N1S) and Sgr B2(N2). We find that propiolamide is at least 50 and 13 times less abundant than acetamide in Sgr B2(N1S) and Sgr B2(N2), respectively, indicating that the abundance difference between both amides is more pronounced by at least a factor of 8 and 2, respectively, than for their corresponding nitriles. Although propiolamide has yet to be included in astrochemical modeling networks, the observed upper limit to the ratio of propiolamide to acetamide seems consistent with the ratios of related species as determined from past simulations. The comprehensive spectroscopic data presented in this paper will aid future astronomical searches.

Dataset Information

Rotational spectroscopic study of S-methyl thioformate: A global laboratory analysis of ground and excited torsional states up to 660 GHz.

Context

Aims

Methods

Results

Conclusions

Publications

Rotational spectroscopic study of S-methyl thioformate: A global laboratory analysis of ground and excited torsional states up to 660 GHz.

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