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Description
The spectra of four low-lying vibrational states of both anti and gauche conformers of n-propyl cyanide were previously measured and analyzed in two spectral windows between 36 and 127GHz. 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 114.4GHz with the Atacama Large Millimeter/Submillimeter Array (ALMA) in its Cycles 0 and 1. We wanted to complete the measurements and analysis up to 506GHz to provide accurate predictions over a much wider range of frequencies, quantum numbers and energies. We recorded new laboratory spectra between 150-270GHz and between 310-506GHz. We carried out analysis over the whole range of measurements available from 36GHz. For the gauche conformer a large number of both a- and b- type transitions were measured, for the anti conformer transitions were predominantly, but not exclusively, a- type We hence improved molecular parameters for the ground state of both anti- and gauche- n-propyl cyanide and for excited vibrational states of the gauche-conformer (v30=1, v29=1, v28=1, v30=2) and anti-conformer (v30=1, v18=1, v29=1, v30=2) with high order coupling parameter determined between v18=1 and v30=2. Parameters are published for the first time for v18=v30=1 for the anti conformer and for v29=v30=1 for the gauche conformer. 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 380GHz. The coupling between v30=2 and v18=1 of the anti conformer has been well characterized. An additional list of 740 lines showing probable but as yet unidentified coupling has been provided for astrophysical identification.
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