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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
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:
FileName Lrecl Records Explanations
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
Note on tables1.dat, tables2.dat: Assignments, observed frequencies, calculated frequencies from the RAM fit, line strengths, and lower energy levels.
See also: J/A+A/538/A51 : Rotational spectrum of CH3CH(NH2)CN (Mollendal+, 2011) Byte-by-byte Description of file: tables?.dat
Bytes Format Units Label Explanations
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)
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)
Acknowledgements: Laurent Margules, laurent.margules(at)univ-lille1.fr
(End) I. Kleiner [LISA], M. Carvajal [U. Huelva], P. Vannier [CDS] 08-Dec-2011
The document above follows the rules of the Standard Description for Astronomical Catalogues.From this documentation it is possible to generate f77 program to load files into arrays or line by line

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