Torsional Line Splittings in the (ν4+ν8)−ν4 Hot Transitions of C2H6 between 1400 and 1510 cm−1

Vibration–rotation–torsion analysis of the high resolution infrared spectrum of C2H6 between 1330 and 1610cm−1: The ν6, ν8, ν4+ν12, 2ν4+ν9 interacting system and hot transitions from ν4 to ν4+ν8

“…[21]. The torsional splittings in the 2m 4 + m 12 state are slightly larger than in 2m 4 , again in agreement with the decrease of the torsional barrier height with the excitation of the m 12 mode.…”

“…In this case, 2m 4 + m 12 was expected to lie more than 20 cm À1 below m 4 + m 8 , because of the high anharmonicity of the torsional mode m 4 . Therefore the crossing for the Fermi-type interaction of these two bands occurs far in the DK = À 1 wings, at K 0 DK between À8 and À9 [21], and its effects in the region of the observed transitions are much less strong than in the corresponding cold system.…”

“…Our analysis relied on spectra for which experimental details regarding their recording, and measurement and calibration of the C 2 H 6 line positions were already described in previous contributions [21,22]. For convenience, they are summarized here.…”

“…In a previous work [21], we identified several hot transitions belonging to the band (m 4 + m 8 ) À m 4 , which were used in calculations aimed to determine the value of the intrinsic torsional splitting in the m 4 + m 8 state. Several features of this band, as some Q subbranches, stand out quite clearly even in moderate and low resolution spectra, and can be relevant in the examination of atmospheric spectra and planetary radiance spectra.…”

“…They obtained sets of effective rotation-torsion-vibration parameters for each of the different Kl-subbranches of m 8 and m 4 + m 12 . More recently, we measured and assigned several hot transitions (m 4 + m 8 ) À m 4 in this spectral region [21]. The analysis of their torsional splittings led to interesting results on the torsional dynamics of ethane-like molecules in the degenerate vibrational states.…”