par Lattanzi, Franca;Di Lauro, Carlo;Vander Auwera, Jean
Référence Journal of Molecular Spectroscopy, 267, 1-2, page (71-79)
Publication Publié, 2011-05
Article révisé par les pairs
Résumé : The Fourier transform infrared spectrum of ethane between 2860 and 3060 cm-1 has been re-investigated under high resolution at 229 K. The infrared absorption in this region is due mainly to the CH stretching fundamentals ν5 (parallel band) and ν7 (degenerate perpendicular band), and to the parallel combination system ν8 + ν11 (A4s, A3s). All the relevant perturbation mechanisms affecting the observed absorption patterns have been clarified. In particular, the main perturbers of the ν7 state are identified to be the degenerate vibrational combination states ν8 + ν11 (l-type interaction) and ν3 + 2ν4 + ν8 (Fermi-type interaction). Because of the last interaction, the K″ΔK = -6 transitions occur with intensities comparable to both the infrared active fundamental ν7 and the almost dark combination ν3 + 2ν4 + ν8. The parallel combination system ν8 + ν11 (A 4s, A3s) is overlapped and heavily perturbed by the nearby parallel system ν4 + ν11 + ν12 (A4s, A3s), whose K-structure is spread by the strong z-Coriolis interaction of its two vibrational components. In this work, 95 new transitions to the perturbers of ν7 have been assigned. They belong mostly to the degenerate vibrational states ν8 + ν11 (E1d) and ν3 + 2ν4 + ν8 (E1d), and to the parallel system ν8 + ν11 (A4s, A3s). A least squares fit calculation, limited to the ν7 degenerate fundamental and its degenerate perturbers ν8 + ν11, ν3 + 2ν4 + ν8, ν4 + ν11 + ν12, and ν3 + 3ν4 + ν12 was performed. From the results of this fit, we created a line-by-line database containing the molecular parameters for 4969 transitions in these five bands of 12C2H6. Finally, we identified the degenerate combination band ν2 + ν8 (62 observed transitions) to be the main perturber (x, y-Coriolis-type interaction) of the parallel fundamental ν5. © 2011 Elsevier Inc. All rights reserved.