J/A+A/493/565 Deuterated and 15N ethyl cyanides (Margules+, 2009)
Rotational spectrum of deuterated and 15N ethyl cyanides: CH3CHDCN,
CH2DCH2CN and CH3CH2C15N.
Margules L., Motiyenko R., Demyk K., Tercero B., Cernicharo J., Sheng M.,
Wiedmann M., Gripp J., Maeder H., Demaison J.
<Astron. Astrophys. 493, 565 (2009)>
=2009A&A...493..565M 2009A&A...493..565M
ADC_Keywords: Atomic physics
Keywords: line: identification - methods: laboratory - molecular data -
ISM: molecules - radio lines: ISM - submillimeter
Abstract:
Ethyl cyanide is an abundant molecule in hot molecular clouds. Its
rotational spectrum is very dense and several hundreds of rotational
transitions within the ground state have been identified in molecular
clouds in the 40-900GHz frequency range. Lines from 13C isotopically
substituted ethyl cyanide have been recently identified in Orion.
To enable the search and the possible detection of other isotopologues
of ethyl cyanide in interstellar objects we have studied the
rotational spectrum of deuterated ethyl cyanide: CH2DCH2CN
(in-plane and out-of-plane) and CH3CHDCN and the spectrum of 15N
substituted ethyl cyanide CH2DCH2C15N.
The rotational spectrum of these species in the ground state was
measured in the microwave and millimeter-submillimeter wavelength
range using waveguide Fourier transform spectrometers (4-40GHz) and a
source-modulated spectrometer employing backward-wave oscillators
(BWOs) (150-260 and 580-660GHz). More than 300 lines were identified
for each species for J values up to 71-80 and Ka values up to 28-31
depending on the isotopologues. The experimental spectra were analysed
using a Watson's Hamiltonian using A-reduction in Ir representation.
From the fitting procedure, accurate spectroscopic constants were
derived for each species. These new sets of spectroscopic constants
enable us to compute reliable prediction of the rotational spectrum
(lines frequency and intensity) in the 4-1000GHz frequency range and
for J and Ka up to 80 and 31, respectively. This experimental study
allowed us to detect for the first time 15N substituted ethyl
cyanide CH2DCH2C15N in Orion. The derived column density and
rotational temperature are 1013cm-2 and 150K for the plateau and
3x1014cm-2 and 300K for the hot core. The deuterated species were
search for but are not detected. The upper limit on the column density
of each deuterated isotopologues is 1014cm-2.
Description:
The tables present the predicted line-center frequency and line
strength of rotational transitions for the 15N-isotopologue of ethyl
cyanide (CH3CH2C15N) and of its deuterated isotopologues:
CH3CHDCN, CH2DCH2CN in-plane and out-of-plane, up to 1THz and
for J<100. 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 a more realistic estimation of the 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
table7.dat 50 13475 Predicted transitions of CH3CH2C15N
table8.dat 50 14292 Predicted transitions of CH3CHDCN
table9.dat 50 13610 Predicted transitions of CH2DCH2CN-in-plane
table10.dat 50 14234 Predicted transitions of CH2DCH2CN-out-of-plane
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See also:
J/A+A/466/255 : Isotopic ethyl cyanide (Demyk+, 2007)
Byte-by-byte Description of file: table*.dat
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Bytes Format Units Label Explanations
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1- 3 I3 --- J0 J value of the lower state
5- 6 I2 --- Ka0 Ka value of the lower state
8- 10 I3 --- Kc0 Kc value of the lower state
12- 13 I2 --- J1 J value of the upper state
15- 16 I2 --- Ka1 Ka value of the upper state
18- 19 I2 --- Kc1 Kc value of the upper state
21- 29 F9.2 MHz Freq Calculated frequency
31- 34 F4.2 MHz e_Freq Error on the calculated frequency
36- 40 F5.2 --- S Line strength
42 A1 --- Dipole [A/B] Type of the transition
44- 50 F7.2 cm-1 E0 Energy of the lower state
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Acknowledgements:
Karine Demyk, demyk(at)cesr.fr
(End) Patricia Vannier [CDS] 24-Nov-2008