Global modeling of vibration-rotation spectra of the acetylene molecule

- Global modeling of C2H2 high resolution spectra in 50-9900 cm−1 range.
- 24,991 observed line positions reproduced with RMS=0.0037 cm−1.
- 8593 line intensities reproduced within their experimental uncertainties 2-20%.
- The performed modeling will be used to generate a high-temperature C2H2 databank.

The global modeling of both line positions and intensities of the acetylene molecule in the 50-9900 cm−1 region has been performed using the effective operators approach. The parameters of the polyad model of effective Hamiltonian have been fitted to the line positions collected from the literature. The used polyad model of effective Hamiltonian takes into account the centrifugal distortion, rotational and vibrational ℓ-doubling terms and both anharmonic and Coriolis resonance interaction operators arising due to the approximate relations between the harmonic frequencies: ω1≈ω3≈5ω4≈5ω5 and ω2≈3ω4≈3ω5. The dimensionless weighted standard deviation of the fit is 2.8. The fitted set of 237 effective Hamiltonian parameters allowed reproducing 24,991 measured line positions of 494 bands with a root mean squares deviation 0.0037 cm−1.The eigenfunctions of the effective Hamiltonian corresponding to the fitted set of parameters were used to fit the observed line intensities collected from the literature for 15 series of transitions: ΔP = 0-13,15, where P=5V1+5V3 +3V2+V4+V5 is the polyad number (Vi are the principal vibrational quantum numbers). The fitted sets of the effective dipole moment parameters reproduce the observed line intensities within their experimental uncertainties 2-20%.