Effective Rotation–Vibration Parameters for the ν8and ν4+ ν12Bands of Ethane

Head and Tail Deformations, Torsional Coriolis Coupling, and E1d-E2d Vibrational Mixing in Ethane-Like Molecules

“…This agrees with the theoretical results of Hougen (13), since the L 1 , L 2 , M 1 and ϪM 2 coordinates defined by Hougen are E 1d ( x), E 1d ( y), E 2d ( y), and E 2d ( x) coordinates, respectively. The torsional Coriolis operator couples the same pairs of components as H (2) , because we have seen in Section III that it couples vibrational components with the same x or y orientation in a molecular frame.…”

“…It can be shown either by symmetry arguments or by calculation that both the torsional Coriolis operator and H (2) obey the torsional selection rule ϩ 7 Ϫ or cos 7 sin, the first operator with ⌬K i ϭ 0 and the second one with ⌬K i ϭ Ϯ6. Therefore the coupling of two E 1d and E 2d vibrational states in a free internal rotor state occurs by the following matrix elements:…”

“…[6], the matrix elements of H (2) between the E 1d ( x) and the E 2d ( y) blocks, with x-oriented coordinates, are opposite to those between the E 1d ( y) and the E 2d ( x) blocks, with y-oriented coordinates. This agrees with the theoretical results of Hougen (13), since the L 1 , L 2 , M 1 and ϪM 2 coordinates defined by Hougen are E 1d ( x), E 1d ( y), E 2d ( y), and E 2d ( x) coordinates, respectively.…”

Weak Combination Bands in the 3-μm Region of Ethane

“…The method of the effective stack-by-stack analysis, following the procedure of Cole et al (6), was already extensively used in our recent work on ethane (15,21,22). We briefly recall here that the transitions within one KЈ 4 KЉ subband are fitted to the expression:…”

“…(3), this results in a Coriolis constant of 9ϩ12 ϭ Ϫ0.65, which yields 12 ϭ ϩ0.39. Finally, we very recently reinvestigated the 8 and 4 ϩ 12 bands, near 1500 cm Ϫ1 (15), and determined from the rotational analysis 4ϩ12 ϭ ϩ0.45, which yields the identical value for 12 . Strong perturbations observed in the latter case should account for the slight difference with the other values reported, all around 12 ϭ ϩ0.40.…”