J/A+A/466/255 Isotopic ethyl cyanide (Demyk+, 2007)
Isotopic ethyl cyanide 13CH3CH2CN, CH313CH2CN, and CH3CH213CN:
laboratory rotational spectrum and detection in Orion.
Demyk K., Maeder H., Tercero B., Cernicharo J., Demaison J., Magules L.,
Wegner M., Keipert S., Sheng M.
<Astron. Astrophys. 466, 255 (2007)>
=2007A&A...466..255D 2007A&A...466..255D
ADC_Keywords: Atomic physics
Keywords: line: identification - methods: laboratory - molecular data -
ISM: molecules - radio lines: ISM - submillimeter
Abstract:
Astronomical spectra of hot molecular clouds in the wavelength range
from centimeter to submillimeter show a huge number of rotational
lines due to the emission of complex organic molecules, and a large
fraction of these lines are unidentified. The assignment of these
unidentified lines to new molecules, to known molecules in excited
states, or to their isotopologues requires a good knowledge of the
spectroscopic parameters of these molecules.
We present the experimental study of the spectroscopic properties of
13C-substituted ethyl cyanide 13CH3CH2CN, CH313CH2CN, and
CH3CH213CN.
The rotational spectra of the three species in the ground state have
been measured in the frequency ranges from 5 to 26GHz using waveguide
Fourier transform spectrometers and from 160 to 360GHz using a
source-modulated spectrometer employing backward-wave oscillators
(BWOs).
A new accurate set of spectroscopic constants has been determined for
each isotopic species. This permits prediction of the position of
rotational lines that are best suited for detection with an accuracy
of a few hundreds of kHz. The three isotopologues have been detected
in an Orion IRc2 IRAM survey via several hundred of lines,
illustrating that many "unidentified" bands are definitely due to
isotopologues of known molecules.
Description:
The tables present the predicted the frequency of rotational
transitions for the three 13C-isotopologues of ethyl cyanide, up to
600GHz and for J<60. The frequencies are calculated using a Watson's
Hamiltonian in A-reduction in Ir representation.
The error on the frequency given in the tables is the standard
deviation. To get an estimate of the "true" error it must be
multiplied by a factor 3, for the strongest lines to 10, for the
weakest lines. However, the general trend is that for the lines that
are the most suitable for interstellar detection, i.e. the strongest
lines having J value up to ∼50 and a low Ka value, the error on the
predicted frequencies is a few hundred kHz, suitable for line
identification in the interstellar spectra. The error is larger for
the weakest lines and increases as J and Ka become larger, i.e., as
the frequency increases.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table6.dat 51 7178 Predicted transitions of 13CH3CH2CN
table7.dat 51 7770 Predicted transitions of CH313CH2CN
table8.dat 51 7157 Predicted transitions of CH3CH213CN
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Byte-by-byte Description of file: table6.dat table7.dat table8.dat
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Bytes Format Units Label Explanations
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1- 2 I2 --- J0 J value of the lower state
4- 5 I2 --- Ka0 Ka value of the lower state
7- 8 I2 --- Kc0 Kc value of the lower state
10- 11 I2 --- J1 J value of the upper state
13- 14 I2 --- Ka1 Ka value of the upper state
16- 17 I2 --- Kc1 Kc value of the upper state
19- 27 F9.2 MHz Freq Calculated frequency
29- 33 F5.2 MHz e_Freq Error on the calculated frequency
35- 41 F7.4 --- S Line strength
43 A1 --- Dipole [A/B] Type of the transition
45- 51 F7.2 cm-1 E0 Energy of the lower state
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Acknowledgements:
Karine Demyk, karine.demyk(at)univ-lille1.fr
(End) Patricia Vannier [CDS] 22-Feb-2007