Perturbation activated transitions in the high resolution infrared spectrum of C2H6: rotational constants and torsional splitting in the ground state

Carlo Di Lauro (1) , Franca Lattanzi (2) , Veli-Matti Horneman (3) , Michel Herman (4) , Jean Vander Auwera (4)

1 Pharmaceutical Chemistry
2 University of Naples Federico II = Università degli studi di Napoli Federico II
3 University of Oulu
4 ULB - Université libre de Bruxelles

The l-type perturbation mechanisms which activate vibration-rotation transitions with Δk = ±2, -Δ(l modulo 3) = ± 1 in the perpendicular bands of molecules with threefold axial symmetry are investigated in the case of ethane-like molecules. It is shown that in this class of molecules such transitions, combined with the usual ones with Δk = Δ(l modulo 3) = ±1, give information not only on the values of the K-structure rotational parameters, but also on the torsional splitting of the lower combining state. We have examined transitions of this type in two perturbed regions of the infrared spectrum of C2H6, in the n8 fundamental and in the n4+n10 combination. Assuming that the four torsional components in the ground state of C2H6 follow the energy pattern generated when tunneling occurs from one minimum of the torsional potential barrier to the two adjacent minima only, we evaluate a torsional splitting of 0.00566 ± 0.00015 cm^-1in each rotational level. We can also determine the values of the ground state rotational constants A"= 2.669693 ±0.000020 cm^{-1 and 105DK" = 0.885± 0.050 cm-1.}

Mots clés: Physical Sciences

Carlo Di Lauro, Franca Lattanzi, Veli-Matti Horneman, Michel Herman, Jean Vander Auwera. Perturbation activated transitions in the high resolution infrared spectrum of C2H6: rotational constants and torsional splitting in the ground state. Molecular Physics, 2007, 105 (05-07), pp.733-740. ⟨10.1080/00268970601110324⟩. ⟨hal-00513061⟩