J/A+A/591/A75 Millimeter wave spectrum of methyl cyanate (Kolesnikova+, 2016)
The millimeter wave spectrum of methyl cyanate: a laboratory study and
astronomical search in space.
Kolesnikova L., Alonso J.L., Bermudez C., Alonso E.R., Tercero B.,
Cernicharo J., Guillemin J.-C.
<Astron. Astrophys. 591, A75 (2016)>
=2016A&A...591A..75K 2016A&A...591A..75K (SIMBAD/NED BibCode)
ADC_Keywords: Interstellar medium ; Spectroscopy ; Atomic physics
Keywords: astrochemistry - line: identification - techniques: spectroscopic -
astronomical databases: miscellaneous - molecular data
Abstract:
The recent discovery of methyl isocyanate (CH3NCO) in Sgr B2(N) and
Orion KL makes methyl cyanate (CH3OCN) a potential molecule in the
interstellar medium. The aim of this work is to fulfill the first
requirement for its unequivocal identification in space, i.e. the
availability of transition frequencies with high accuracy.
The room-temperature rotational spectrum of methyl cyanate was
recorded in the millimeter wave domain from 130 to 350GHz. All
rotational transitions revealed A-E splitting owing to methyl internal
rotation and were globally analyzed using the ERHAM program.
The data set for the ground torsional state of methyl cyanate exceeds
700 transitions within J"=10-35 and K"a=0-13 and newly derived
spectroscopic constants reproduce the spectrum close to the
experimental uncertainty. Spectral features of methyl cyanate were
then searched for in Orion KL, Sgr B2(N), B1-b, and TMC-1 molecular
clouds. Upper limits to the column density of methyl cyanate are
provided.
Description:
Observed and predicted rotational transition frequencies of methyl
cyanate in the ground torsional state.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
tables1.dat 39 738 Observed rotational transition frequencies of
methyl cyanate in the ground torsional state
tables2.dat 62 1962 Predicted rotational transition frequencies of
methyl cyanate in the ground torsional state
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Byte-by-byte Description of file: tables1.dat
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Bytes Format Units Label Explanations
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1 I1 --- Sigma [0/1] Symmetry number (1)
3- 4 I2 --- J1 Upper state J quantum number (J')
6- 7 I2 --- Ka1 Upper state Ka quantum number (Ka')
9- 10 I2 --- Kc1 Upper state Kc quantum number (Kc')
12- 13 I2 --- J0 Lower state J quantum number (J")
15- 16 I2 --- Ka0 Lower state Ka quantum number (Ka")
18- 19 I2 --- Kc0 Lower state Kc quantum number (Kc")
21- 30 F10.3 MHz FreqObs Observed transition frequency
32- 37 F6.3 MHz O-C Observed minus calculated frequency
39 A1 --- Comment Comment (2)
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Note (1): The symmetry numbers sigma = 0 and 1 label the A and E transitions,
respectively.
Note (2): Blended transitions are indicated using the capital letter B.
In case of the lines composed from degenerate asymmetric rotor
transitions, equal weights were assigned to the components of such
blends. Any other transitions blended accidentally, as those
corresponding to not related A and E components, were not included
in the fit. The capital letter E indicates the excluded transitions.
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Byte-by-byte Description of file: tables2.dat
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Bytes Format Units Label Explanations
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1 I1 --- Sigma [0/1] Symmetry number (1)
3- 4 I2 --- J1 Upper state J quantum number (J')
6- 7 I2 --- Ka1 Upper state Ka quantum number (Ka')
9- 10 I2 --- Kc1 Upper state Kc quantum number (Kc')
12- 13 I2 --- J0 Lower state J quantum number (J")
15- 16 I2 --- Ka0 Lower state Ka quantum number (Ka")
18- 19 I2 --- Kc0 Lower state Kc quantum number (Kc")
21- 30 F10.3 MHz FreqPred Predicted frequency
32- 36 F5.3 MHz e_FreqPred Uncertainty of the predicted frequency (2)
38- 46 F9.5 D+2 Smu2 Intensity (3)
48- 54 F7.3 cm-1 E1 Upper level energy (E') (4)
56- 62 F7.3 cm-1 E0 Lower level energy (E")
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Note (1): The symmetry numbers sigma = 0 and 1 label the A and E transitions,
respectively.
Note (2): Only transitions with uncertainty <1MHz are included.
Note (3): Given in terms of calculated line strengths multiplied by the square
of the corresponding dipole moment component.
Note (4): The upper state energies refer to a hypothetical unsplit J=0 energy
level.
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Acknowledgements:
Lucie Kolesnikova, lucie.kolesnikova(at)uva.es
(End) Lucie Kolesnikova [GEM, UVa, Spain], Patricia Vannier [CDS] 04-May-2016