J/A+A/538/A119 Spectrum of 18O-methyl formate (HCO18OCH3) (Tercero+ 2012)
Microwave and sub-mm spectroscopy and first ISM detection of 18O-methyl formate.
Tercero B., Margules L., Carvajal M., Motiyenko R.A., Huet T.R.,
Alekseev E.A., Kleiner I., Guillemin J.C., Mollendal H., Cernicharo J.
<Astron. Astrophys. 538, A119 (2012)>
=2012A&A...538A.119T 2012A&A...538A.119T
ADC_Keywords: Interstellar medium ; Spectroscopy
Keywords: astrochemistry - ISM: molecules - submillimeter: ISM -
line: identification - astronomical databases: miscellaneous -
ISM: individual objects: Orion KL
Abstract:
Astronomical survey of interstellar molecular clouds needs a previous
analysis of the spectra in the microwave and sub-mm energy range of
organic molecules in order to be able to identify them. Very accurate
spectroscopic constants are obtained in a comprehensive laboratory
analysis of rotational spectra. These constants can be used to predict
with very high precision the frequencies of transitions that have not
been measured in the laboratory.
In this work, an experimental study and its theoretical analysis is
presented for two 18O-methyl formate isotopologues in order to detect
for the first time both isotopologues in Orion KL. The experimental
spectra of both isotopologues of methyl formate have been recorded in
the microwave and sub-mm energy range from 1 to 660GHz. Both spectra
have been analysed by using the Rho-Axis Method (RAM) which takes into
account the CH3 internal rotation. Spectroscopic constants of both
18O-methyl formate have been obtained with high accuracy. Thousands
of transitions were assigned and others predicted, which allowed us to
detect both species in the IRAM 30m line survey of Orion KL for the
first time in the space.
Description:
The two 18O isotopic species of methyl formate were measured and
analysed up to 660GHz. The treatment of the internal rotation motion
was made using the Rho-Axis- Method and the BELGI code. 4430 and 3258
lines are assigned for the ground torsional states from the
HCO18OCH3 and HC18OOCH3 species, respectively. From these
spectral analysis, accurate predictions of line positions and
intensities are performed.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
tables1.dat 105 19073 *Data for 18O-methyl formate (HCO18OCH3)
microwave transitions from vt=0 torsional state
included in the fit with parameters of Table 4
tables2.dat 105 18053 *Data for 18O-methyl formate (HC18OOCH3)
microwave transitions from vt=0 state included in
the fit with parameters of Table 5
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Note on tables1.dat, tables2.dat: Assignments, observed frequencies, calculated
frequencies from the RAM fit, line strengths, and lower energy levels.
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See also:
J/A+A/500/1109 : Rotational spectrum of HCOO13CH3 (Carvajal+, 2009)
J/ApJ/714/1120 : Rotational spectrum and DCOOCH3 in Orion (Margules+, 2010)
J/ApJS/190/315 : Rotational spectrum of H13COOCH3 (Carvajal+, 2010)
J/A+A/538/A51 : Rotational spectrum of CH3CH(NH2)CN (Mollendal+, 2011)
J/A+A/568/A58 : HCOO13CH3 rotational spectrum (Haykal+, 2014)
Byte-by-byte Description of file: tables?.dat
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Bytes Format Units Label Explanations
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1- 6 I6 --- LNum [1/123367] Line number (1)
9- 10 I2 --- vt' [0] upper torsional quantum number (2)
12- 14 I3 --- J' [1/63] upper total angular momentum (2)
16- 18 I3 --- Ka' [-34/31] upper Ka rotational quantum number (2)
21- 22 I2 --- Kc' [0/63] upper Kc rotational quantum number (2)
24 A1 --- p' [±] upper parity (2)
27- 28 I2 --- vt" [0] lower torsional quantum number (2)
30- 32 I3 --- J" [1/63] lower total angular momentum (2)
34- 36 I3 --- Ka" [-34/31] lower Ka rotational quantum number (2)
39- 40 I2 --- Kc" [0/63] lower Kc rotational quantum number (2)
42 A1 --- p" [±] lower parity (2)
46- 55 F10.3 MHz oFreq [1630/660000]? Observed frequency
57- 61 F5.3 MHz e_oFreq ? Uncertainty in oFreq
66- 75 F10.3 MHz cFreq [1000/660000] Calculated frequency
77- 82 F6.3 MHz e_cFreq Uncertainty in cFreq
89- 95 F7.3 D+2 Lstr Line strength; see text for details
97-105 F9.4 cm-1 Elow Lower state energy (3)
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Note (1): The first column is a line number, allowing to sort the lines by
J and K sub-branches if needed.
Note (2): Upper and lower state quantum numbers are indicated by ' and "
respectively. Torsion-rotation levels of A species have a "parity"
label; levels of E species have a signed Ka value (Herbst et al.,
1984, J. Mol. Spectrosc., 108, 42). Note that for certain degenerate
transitions, the sum of line strengths of the degenerate transitions
for a given cluster is preserved.
Note (3): Lower state energy (cm-1) refered to the J=Ka=0 A-species energy
level taken as the zero of the energy (zero point torsional energy:
66.27348cm-1 for tables1.dat, 66.29250cm-1 for tables2.dat)
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Acknowledgements:
Laurent Margules, laurent.margules(at)univ-lille1.fr
(End) I. Kleiner [LISA], M. Carvajal [U. Huelva], P. Vannier [CDS] 08-Dec-2011