Precise ro-vibrational analysis of molecular bands forbidden in absorption: The [formula omitted] band of the 12C2H4 molecule

Abstract

The highly accurate (experimental accuracy in line positions ∼(1-2)×10-4cm−1) ro-vibrational spectrum of the ν8+ν10 band of the 12C2H4 molecule was recorded for the first time with high resolution Fourier transform spectrometry and analyzed in the region of 1650–1950cm−1 using the Hamiltonian model which takes into account Coriolis resonance interactions between the studied ν8+ν10 band, which is forbidden in absorption, and the bands ν4+ν8 and ν7+ν8. About 1570 transitions belonging to the ν8+ν10 band were assigned in the experimental spectra with the maximum values of quantum numbers Jmax.=35 and Kamax.=18. On that basis, a set of 38 vibrational, rotational, centrifugal distortion, and resonance interaction parameters was obtained from the fit. They reproduce values of 598 initial “experimental” ro-vibrational energy levels (positions of about 1570 experimentally recorded and assigned transitions) with the rms error drms=0.00045cm−1 (drms=0.00028cm−1 when upper ro-vibrational energies obtained from blended and very weak transitions were deleted from the fit).