High-resolution spectroscopy and preliminary global analysis of C-H stretching vibrations of C2H4 in the 3000 and 6000 cm regions

Ethylene (ethene, H₂C=CH₂) is a naturally occurring compound in ambient air that affects atmospheric chemistry and global climate. The C₂H₄ spectrum is available in databases only for the 1000 and 3000 cm⁻¹ ranges.In this work, the ethylene absorption spectrum was measured in the 6030-6250 cm⁻¹ range with the use of a high resolution Bruker IFS 125HR Fourier-spectrometer and a two-channel opto-acoustic spectrometer with a diode laser. As a secondary standard of wavelengths, the methane absorption spectrum was used in both cases.A preliminary analysis was realized thanks to the tensorial formalism developed by the Dijon group that is implemented in the XTDS software package [39]. We considered the two combination bands ν₅+ν₉ and ν₅+ν₁₁ as an interacting dyad. Parameters for the ν₉/ν₁₁ dyad were fitted simultaneously from a re-analysis of previously recorded supersonic expansion jet FTIR data, while parameters for the v₅=1 Raman level were taken from literature. More than 600 lines could be assigned in the 6030-6250 cm⁻¹ region (and also 682 in the 2950-3150 cm⁻¹ region) and effective Hamiltonian parameters were fitted, including Coriolis interaction parameters. The dyad features are globally quite well reproduced, even if there are still problems at high J values.