Rotational rest frequencies of the low lying vibrational states of n-propyl cyanide from extensive laboratory measurements up to 506 GHz⋆
IRAP, Université de Toulouse, CNRS, CNES, UPS, 9 Av. Colonel Roche, BP 44346, 31028 Toulouse Cedex 4, France
2 I. Physikalisches Institut, Universität zu Köln, Zülpicher Str. 77, 50937 Köln, Germany
Accepted: 9 December 2018
Context. The spectra of four low-lying vibrational states of both anti and gauche conformers of normal-propyl cyanide were previously measured and analyzed in two spectral windows between 36 and 127 GHz. All states were then identified in a spectral line survey called Exploring Molecular Complexity with ALMA (EMoCA) toward Sagittarius B2(N) between 84.1 and 114.4 GHz with the Atacama Large Millimeter/submillimeter Array (ALMA) in its Cycles 0 and 1.
Aims. We wanted to extend the measurements and analysis up to 506 GHz to provide accurate predictions over a much wider range of frequencies, quantum numbers and energies.
Methods. We carried out measurements in two additional frequency windows up to 506 GHz.
Results. For the gauche conformer, a large number of both a- and b-type transitions were identified. For the anti conformer, transitions were predominantly, but not exclusively, a-type. We hence improved molecular parameters for the ground states of both anti- and gauche-n-propyl cyanide and for excited vibrational states of the gauche conformer (v30 = 1, v29 = 1, v30 = 2, v28 = 1) and anti conformer (v30 = 1, v18 = 1, v30 = 2, v29 = 1) with high order coupling parameters determined between v18 = 1 and v30 = 2. Parameters are published for the first time for v18 = v30 = 1 of the anti conformer and for v29 = v30 = 1 of the gauche conformer.
Conclusions. In total 15385 lines have been incorporated in the fits and should allow good predictions for unperturbed lines over the whole operating range of radio-telescopes. Evidence is found for vibrational coupling for some levels above 380 GHz. The coupling between v18 = 1 and v30 = 2 of the anti conformer has been well characterized. An additional list of 740 lines showing potential but as yet unidentified coupling has been provided for astrophysical identification.
Key words: molecular data / line: identification / astrochemistry / methods: laboratory: molecular / ISM: molecules / submillimeter: ISM
Line lists (Tables 10–25) are only available at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (18.104.22.168) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/622/A82
© ESO 2019
Open Access article, published by EDP Sciences, under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.