Accurate Spectroscopic Characterization of Ethyl Mercaptan and Dimethyl Sulfide Isotopologues: A Route Toward Their Astrophysical Detection

Puzzarini, Cristina; Senent, María Luisa; Domı́nguez-Gómez, R.; Carvajal, M.; Hochlaf, M.; Al‐Mogren, Muneerah Mogren

doi:10.1088/0004-637x/796/1/50

Cited by 16 publications

(13 citation statements)

References 48 publications

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“…We have also determined spectroscopic parameters of the anti conformer using Watson's A reduction for comparison purposes with parameters of Kolesniková et al (2014) and with values from quantum chemical calculations (Puzzarini et al 2014). These parameters are given in Table 5.…”

Section: Fig 2 Same As Inmentioning

confidence: 99%

“…For example, ∼23 and ∼18 Hz were obtained for the anti conformers of the two isotopomers of ethanol with one 13 C (Bouchez et al 2012), ∼13.5 Hz for dimethyl ether with 0 (Endres et al 2009), 1, and 2 13 C atoms (Koerber et al 2013), and 93 Hz for propargyl alcohol (Pearson & Drouin 2005). Therefore, we suspect that there are errors in the quantum chemical calculations of sextic distortion parameters in Puzzarini et al (2014).…”

Section: Fig 2 Same As Inmentioning

confidence: 99%

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Exploring molecular complexity with ALMA (EMoCA): Alkanethiols and alkanols in Sagittarius B2(N2)

Müller

Беллоче

et al. 2016

A&A

139

157

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Context. Over the past five decades, radio astronomy has shown that molecular complexity is a natural outcome of interstellar chemistry, in particular in star forming regions. However, the pathways that lead to the formation of complex molecules are not completely understood and the depth of chemical complexity has not been entirely revealed. In addition, the sulfur chemistry in the dense interstellar medium is not well understood. Aims. We want to know the relative abundances of alkanethiols and alkanols in the Galactic center source Sagittarius B2(N2), the northern hot molecular core in Sgr B2(N), whose relatively small line widths are favorable for studying the molecular complexity in space. Methods. We investigated spectroscopic parameter sets that were able to reproduce published laboratory rotational spectra of ethanethiol and studied effects that modify intensities in the predicted rotational spectrum of ethanol. We used the Atacama Large Millimeter Array (ALMA) in its Cycles 0 and 1 for a spectral line survey of Sagittarius B2(N) between 84 and 114.4 GHz. These data were analyzed by assuming local thermodynamic equilibrium (LTE) for each molecule. Our observations are supplemented by astrochemical modeling; a new network is used that includes reaction pathways for alkanethiols for the first time. Results. We detected methanol and ethanol in their parent 12 C species and their isotopologs with one 12 C atom substituted by 13 C; the latter were detected for the first time unambiguously in the case of ethanol. The 12 C/ 13 C ratio is ∼25 for both molecules. In addition, we identified CH OH ratio of ∼7.3. Upper limits were derived for the next larger alkanols normal-and iso-propanol. We observed methanethiol, CH 3 SH, also known as methyl mercaptan, including torsionally excited transitions for the first time. We also identified transitions of ethanethiol (or ethyl mercaptan), though not enough to claim a secure detection in this source. The ratios CH 3 SH to C 2 H 5 SH and C 2 H 5 OH to C 2 H 5 SH are 21 and 125, respectively. In the process of our study, we noted severe discrepancies in the intensities of observed and predicted ethanol transitions and propose a change in the relative signs of the dipole moment components. In addition, we determined alternative sets of spectroscopic parameters for ethanethiol. The astrochemical models indicate that substantial quantities of both CH 3 SH and C 2 H 5 SH may be produced on the surfaces of dust grains, to be later released into the gas phase. The modeled ratio CH 3 SH/C 2 H 5 SH = 3.1 is lower than the observed value of 21; the model value appears to be affected most by the underprediction of CH 3 SH relative to CH 3 OH and C 2 H 5 OH, as judged by a very high CH 3 OH/CH 3 SH ratio. Conclusions. The column density ratios involving methanol, ethanol, and methanethiol in Sgr B2(N2) are similar to values reported for Orion KL, but those involving ethanethiol are significantly different and suggest that the detection of ethanethiol reported toward Orion KL ...

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Section: Fig 2 Same As Inmentioning

confidence: 99%

Section: Fig 2 Same As Inmentioning

confidence: 99%

Exploring molecular complexity with ALMA (EMoCA): Alkanethiols and alkanols in Sagittarius B2(N2)

Müller

Беллоче

et al. 2016

A&A

139

157

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“…Finally, using state-of-the-art computational methodologies, Puzzarini et al (2014) also predict a set of reliable rotational and torsional parameters for the monosubstituted isotopologues of DMS as well as ethyl mercaptan. The present paper aims at completing the microwave, millimeter wave and FIR dataset of DMS to produce a reliable linelist for astronomical purposes.…”

Section: Introductionmentioning

confidence: 99%

Laboratory microwave, millimeter wave and far-infrared spectra of dimethyl sulfide

Jabri

Van

Nguyen

et al. 2016

A&A

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Context. Dimethyl sulfide, CH 3 SCH 3 (DMS), is a nonrigid, sulfur-containing molecule whose astronomical detection is considered to be possible in the interstellar medium. Very accurate spectroscopic constants were obtained by a laboratory analysis of rotational microwave and millimeter wave spectra, as well as rotation-torsional far-infrared (FIR) spectra, which can be used to predict transition frequencies for a detection in interstellar sources. Aims. This work aims at the experimental study and theoretical analysis of the ground torsional state and ground torsional band ν 15 of DMS in a large spectral range for astrophysical use. Methods. The microwave spectrum was measured in the frequency range 2−40 GHz using two Molecular Beam Fourier Transform MicroWave (MB-FTMW) spectrometers in Aachen, Germany. The millimeter spectrum was recorded in the 50−110 GHz range. The FIR spectrum was measured for the first time at high resolution using the FT spectrometer and the newly built cryogenic cell at the French synchrotron SOLEIL. Results. DMS has two equivalent methyl internal rotors with a barrier height of about 730 cm −1 . We performed a fit, using the XIAM and BELGI-C s -2Tops codes, that contained the new measurements and previous transitions reported in the literature for the ground torsional state ν t = 0 (including the four torsional species AA, AE, EA and EE) and for the ground torsional band ν 15 = 1 ← 0 (including only the AA species). In the microwave region, we analyzed 584 transitions with J ≤ 30 of the ground torsional state ν t = 0 and 18 transitions with J ≤ 5 of the first excited torsional state ν t = 1. In the FIR range, 578 transitions belonging to the torsional band ν 15 = 1 ← 0 with J ≤ 27 were assigned. Totally, 1180 transitions were included in a global fit with 21 accurately determined parameters. These parameters can be used to produce a reliable line-list for an astrophysical detection of DMS.

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“…This paper is our third one of a series concerning astrophysically relevant sulfur organic molecules and focusing on their spectroscopic characterization at low temperatures using highly correlated ab initio methods. 3,4 The species under consideration are sulfur-analogs (S-analogs) of well-known Ocontaining astrophysical molecules such as alcohols, ethers, ketones, etc.) 3 that are abundant interstellar species detected very early.…”

Section: Introductionmentioning

confidence: 99%

“…7 In parallel to this fruitful observation, we have published our theoretical study on the main isotopic species of ethyl mercaptan and dimethyl sulfide, 3 while the paper on the corresponding rare isotopic species has been submitted for publication. 4 The present paper is devoted to the S-analogs of methyl formate, 9 which is one of the most relevant astrochemical non-rigid organic molecules. Its cosmological abundance has permitted its detection in the vibrational ground state and in the first and second excited torsional states.…”

Section: Introductionmentioning

confidence: 99%

Theoretical spectroscopic characterization at low temperatures of S-methyl thioformate and O-methyl thioformate

Senent

Puzzarini

Hochlaf

et al. 2014

The Journal of Chemical Physics

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Highly correlated ab initio methods are employed to determine spectroscopic properties at low temperatures of two S-analogs of methyl formate: S-methyl thioformate CH3-S-CHO (MSCHO) and O-methyl thioformate CH3-O-CHS (MOCHS). Both species are detectable and they are expected to play an important role in Astrochemistry. Molecular properties are compared with those of the O-analog, methyl formate. Both isomers present two conformers cis and trans. cis-CH3-S-CHO represents the most stable structure lying 4372.2 cm(-1) below cis-CH3-O-CHS. The energy difference between the cis and trans forms is drastically lower for MSCHO (1134 cm(-1)) than for MOCHS (1963.6 cm(-1)). Harmonic and anharmonic fundamentals and the corresponding intensities, as well as the rotational constants for the ground vibrational and first excited torsional states and the centrifugal distortions constants, are provided. Low torsional energy levels have been obtained by solving variationally a two dimensional Hamiltonian expressed in terms of the two torsional degrees of freedom. The corresponding 2D potential energy surfaces have been computed at the CCSD(T)/aug-cc-pVTZ level of theory. The methyl torsional barriers V3(cis) are determined to be 139.7 cm(-1) (CH3-S-CHO) and 670.4 cm(-1) (CH3-O-CHS). The A/E splitting of ground torsional state has been estimated to be 0.438 cm(-1) for CH3-S-CHO and negligible for CH3-O-CHS.

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Accurate Spectroscopic Characterization of Ethyl Mercaptan and Dimethyl Sulfide Isotopologues: A Route Toward Their Astrophysical Detection

Cited by 16 publications

References 48 publications

Exploring molecular complexity with ALMA (EMoCA): Alkanethiols and alkanols in Sagittarius B2(N2)

Exploring molecular complexity with ALMA (EMoCA): Alkanethiols and alkanols in Sagittarius B2(N2)

Laboratory microwave, millimeter wave and far-infrared spectra of dimethyl sulfide

Theoretical spectroscopic characterization at low temperatures of S-methyl thioformate and O-methyl thioformate

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