J/A+A/639/A129 Ethyl methyl sulfide rotational spectroscopy (Cabezas+, 2020)
The millimeter-wave spectrum and astronomical search for ethyl methyl sulfide.
Cabezas C., Bermudez C., Tercero B., Cernicharo J.
<Astron. Astrophys. 639, A129 (2020)>
=2020A&A...639A.129C 2020A&A...639A.129C (SIMBAD/NED BibCode)
ADC_Keywords: Atomic physics
Keywords: ISM: molecules - methods: laboratory: molecular - molecular data -
line: identification
Abstract:
Sulfur-containing molecules constitute only 8% of the molecules
observed in the interstellar medium (ISM) in spite that sulfur has
been shown to be an abundant element in the ISM. In order to
understand the chemical behaviour of the ISM and specific cases like
the missing sulfur reservoir, a detailed chemical molecular
composition in the ISM must be mapped out.
Our goal is the investigation of the rotational spectrum of ethyl
methyl sulfide, CH3CH2SCH3, which seems to be a potential
candidate to be observed in the ISM since the simpler analogs, CH3SH
and CH3CH2SH, have been already detected. Rotational spectrum of
ethyl methyl sulfide has been observed before, but its experimental
rotational parameters are not precise enough to allow its detection in
the ISM.
The rotational spectrum of ethyl methyl sulfide in the frequency range
72-116.5GHz was measured using a broadband millimeter-wave
spectrometer based on radio astronomy receivers with fast Fourier
transform backends. The spectral searches and identification of the
vibrational excited states of ethyl methyl sulfide was supported by
high-level ab initio calculations on the harmonic and anharmonic force
fields.
The rotational spectra for the trans and gauche conformers of
ethyl methyl sulfide was analyzed and a total of 172 and 259
rotational transitions were observed for each one, respectively. The
observation of A-E internal rotation splittings allowed the
experimental determination of the V3 hindered internal rotation
barrier height for both trans and gauche species. In addition, the
vibrational excited states, resulting from the lowest frequency
vibrational mode nu30 were identified for both conformers. The new
experimental rotational parameters were employed to search for ethyl
methyl sulfide in the cold and warm molecular clouds Orion KL, Sgr
B2(N), B1-b and TMC-1, using the spectral surveys captured by IRAM 30m
at 3mm and 2mm.
Description:
tablea1.dat contains rotational transitions for the ground state of
the trans conformer of EMS
tablea2.dat contains rotational transitions for the ground state of
the gauche conformer of EMS
tablea3.dat contains rotational transitions for the nu30 vibrationally
excited state of ground state of the trans conformer of EMS
tablea4.dat contains rotational transitions for the 2nu30
vibrationally excited state of ground state of the trans conformer of
EMS
tablea5.dat contains rotational transitions for the nu30 vibrationally
excited state of ground state of the gauche conformer of EMS
tablea6.dat contains the predicted transition frequencies for trans
EMS up to 200GHz.
tablea7.dat contains the predicted transition frequencies for gauche
EMS up to 200GHz.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
tablea1.dat 44 207 Measured transitions for
trans ethyl methyl sulfide
tablea2.dat 44 329 Measured transitions for
gauche ethyl methyl sulfide
tablea3.dat 44 61 Measured transitions for
n30 trans ethyl methyl sulfide
tablea4.dat 44 18 Measured transitions for
2n30 trans ethyl methyl sulfide
tablea5.dat 44 43 Measured transitions for
n30 gauche ethyl methyl sulfide
tablea6.dat 45 4988 Predicted frequencies for
trans ethyl methyl sulfide up to 200GHz
tablea7.dat 45 10752 Predicted frequencies for
gauche ethyl methyl sulfide up to 200GHz
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Byte-by-byte Description of file: tablea[12345].dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 2 I2 --- J' Quantum number J for upper level
4- 5 I2 --- Ka' Quantum number Ka for upper level
7- 8 I2 --- Kc' Quantum number Kc for upper level
10- 11 I2 --- J" Quantum number J for lower level
13- 14 I2 --- Ka" Quantum number Ka for lower level
16- 17 I2 --- Kc" Quantum number Kc for lower level
19 A1 --- A-E Internal rotation sub-state
(only in tables A1-A3)
21- 31 F11.4 MHz FreqMeas Measured frequency
33- 38 F6.3 MHz O-C Difference between observed & calculated
frequency
40- 44 F5.3 MHz Uncert Uncertainty associated to frequency
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Byte-by-byte Description of file: tablea6.dat tablea7.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 2 I2 --- J' Quantum number J for upper level
4- 5 I2 --- Ka' Quantum number Ka for upper level
7- 8 I2 --- Kc' Quantum number Kc for upper level
10- 11 I2 --- J" Quantum number J for lower level
13- 14 I2 --- Ka" Quantum number Ka for lower level
16- 17 I2 --- Kc" Quantum number Kc for lower level
19- 20 I2 --- Sym Internal rotation sub-state
23- 33 F11.4 MHz Freq Frequency
39- 45 F7.4 [nm2/MHz] logInt Base 10 logarithm of the integrated intensity
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Acknowledgements:
Carlos Cabezas, carlos.cabezas(at)csic.es
(End) Patricia Vannier [CDS] 10-Jun-2020