J/A+A/541/A121 Three conformers of n-butyl cyanide (Ordu+, 2012)
The quest for complex molecules in space: Laboratory spectroscopy of n-butyl
cyanide, n-C4H9CN, in the millimeter wave region and astronomical search
in Sagittarius B2(N).
Ordu M.H., Mueller H.S.P., Walters A., Nunez M., Lewen F., Belloche A.,
Menten K.M., Schlemmer S.
<Astron. Astrophys. 541, A121 (2012)>
=2012A&A...541A.121O 2012A&A...541A.121O
ADC_Keywords: Atomic physics
Keywords: molecular data - methods: laboratory - techniques: spectroscopic -
radio lines: ISM - ISM: molecules -
ISM: individual objects: Sagittarius B2
Abstract:
The saturated n-propyl cyanide has recently been detected in
Sagittarius B2(N). The next larger unbranched alkyl cyanide is
n-butyl cyanide. We want to provide accurate rest frequency
predictions beyond the millimeter wave range to search for this
molecule in the Galactic center source Sagittarius B2(N) and
facilitate its detection in space. The laboratory rotational spectrum
of n-butyl cyanide has been investigated between 75 and 348GHz. We
have searched for emission lines caused by the molecule in our
sensitive IRAM 30m molecular line survey of Sagittarius B2(N). More
than one thousand rotational transitions have been identified in the
laboratory for each of the three conformers for which limited data had
been obtained previously in a molecular beam microwave study. The
quantum number range has been greatly extended to J∼120 or more and
Ka>35, resulting in accurate spectroscopic parameters and accurate
rest frequency calculations up to about 500GHz for strong to
moderately weak transitions of the two lower energy conformers. Upper
limits of the column densities of N≤3x1015cm-2 and 8x1015cm-2
were derived towards Sagittarius B2(N) for the two lower energy
conformers, anti-anti and gauche-anti, respectively. The present data
will be helpful to identify n-butyl cyanide at millimeter or longer
wavelengths with radio telescope arrays such as ALMA, NOEMA, or EVLA.
In particular, its detection in Sagittarius B2(N) with ALMA seems
feasible.
Description:
Three conformers of n-butyl cyanide have been studied in this work,
anti-anti (AA), gauche-anti (GA), and anti-gauche (AG). The molecules
are asymmetric top rotors. 14N hyperfine structure has been observed
in part in previous work. Watson's S-reduction was used in the
representation Ir. Data below 22GHz are from previous work; data
above 75GHz are from this work. The total spin-angular momentum
quantum number F has only been given for transitions for which 14N
hyperfine structure was resolved. Blended lines (identical transition
frequencies for two or more transitions) were treated as
intensity-weighted averages. In these cases, these weights have been
given in the last column.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table3.dat 60 2308 Measured lines for the anti-anti conformer
table4.dat 60 2285 Measured lines for the gauche-anti conformer
table5.dat 60 1421 Measured lines for the anti-gauche conformer
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See also:
J/A+A/466/255 : Isotopic ethyl cyanide (Demyk+, 2007)
J/A+A/493/565 : Deuterated and 15N ethyl cyanides (Margules+, 2009)
J/ApJS/184/133 : New ground-state measurements of ethyl cyanide (Brauer+, 2009)
Byte-by-byte Description of file: table3.dat table4.dat table5.dat
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Bytes Format Units Label Explanations
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1- 3 I3 --- J" [1/136] Upper J quantum number
5- 6 I2 --- Ka" [0/47] Upper Ka quantum number
8- 10 I3 --- Kc" [0/136] Upper Kc quantum number
12 I1 --- F" [0/9]? Upper F quantum number
14- 16 I3 --- J' [0/135] Lower J quantum number
18- 19 I2 --- Ka' [0/47] Lower Ka quantum number
21- 23 I3 --- Kc' [0/136] Lower Kc quantum number
25 I1 --- F' [0/9]? Lower F quantum number
27- 37 F11.4 MHz Freq [4000/350000] Observed transition frequency
39- 43 F5.3 MHz e_Freq Uncertainty of measurements
46- 53 F8.5 MHz O-C Observed - Calculated frequencies
55- 60 F6.4 --- Weight [0/1]? Weight for blended lines
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Acknowledgements:
Holger S. P. Muller, hspm(at)ph1.uni-koeln.de
(End) H. Muller, [I. Phys. Inst., Koeln, Germany], P. Vannier [CDS] 12-Mar-2012