High resolution study of the v ₇ + v ₈ band of ethylene (C₂H₄) at 1889 cm^-1

Abstract

The v 7 + vs A-type band of C~H4 has been recorded between 1932 and 1847 cm -1 with a resolution of 0"06 cm -x. The transitions with K_l~<8 and J ~< 25 have been assigned. Although slight Coriolis resonances perturb the band, the analysis has been made easy through the use of an elaborate set of asymmetric top computer programmes. The band centre and a set of upper state constants have been obtained. With these constants, 288 observed upper state energy levels have been fitted with a standard deviation of 0-021 cm -1.Using very simple expressions, we have predicted all the resonance effects perturbing the levels of ethylene near 2000 cm -1. This led us to the identification of the v4 + vs and vs + vt0 combination bands in low resolution spectra.

The high-resolution infrared spectrum of ethylene in the 1800–2350 cm−1spectral region

“…As found previously [13] as well as observed in this work, a large number of resonances perturb the ro-vibrational levels of the polyad of interacting states {8 1 10 1 , 7 1 8 1 , 4 1 8 1 , 8 1 12 1 , 6 1 10 1 , 6 1 7 1 , 4 1 6 1 , 3 1 10 1 , 3 1 7 1 }. We describe them here in some detail in order to demonstrate the resonance scheme used to build the Hamiltonian matrix.…”

“…We initially started the assignment process dealing with the strong ν 7 + ν 8 band, but, as pointed out in refs. [13][14][15], it soon became obvious that its transitions are strongly perturbed by ν 4 + ν 8 transitions through a C-type Coriolis interaction via the ξ a 7,10 and ξ b 4,10 Coriolis interaction terms [10]. In addition, we observed other interactions with the 8 1 10 1 and 8 1 12 1 energy levels which correspond with what has been observed at 10 µm where the polyad of interacting states {10 1 , 8 1 , 7 1 , 12 1 } was considered.…”

“…Using a Hamiltonian matrix taking into account the necessary interaction terms, it was possible to assign many lines of ν 7 + ν 8 and ν 4 + ν 8 . During this process, it became very clear that the ro-vibrational levels of 4 1 8 1 and 7 1 8 1 are also perturbed by nearby rotational levels from bands belonging to other polyads [13]. We then started to assign transitions belonging to these other bands: ν 6 + ν 10 , ν 6 + ν 7 , ν 4 + ν 6 and ν 3 + ν 10 .…”

“…therein, 11-12]. Nevertheless, prior to this work, only small portions of the 4.3 µm to 5.6 µm region, corresponding to the ν 7 + ν 8 and ν 4 + ν 8 bands have been analyzed [13][14][15]. More recently, three high-resolution infrared and Raman spectra of 12 C 2 H 4 were recorded and analyzed: the ν 12 band near 1450 cm -1 [16], the 2ν 10 overtone symmetric motion located around 1664 cm -1 [17] and the C-H stretching vibrations in the 3000 and 6000 cm -1 regions [18].…”

CO Laser Absorption Coefficients for Gases of Biological Relevance: H2O, CO2, Ethanol, Acetaldehyde, and Ethylene

“…22 The absorption coef® cients for ethylene were determined by mixing, with the use of electronic m ass¯ow controllers, gaseous ethylene with the carrier gas to a concentration of a few hundred parts per m illion.…”