High-resolution FTIR spectroscopy of the v₁₁ and v₂ + v₇ bands of ethylene-d₄

Abstract

The Fourier transform infrared spectrum of the v₁₁ band of ethylene-d₄ (C₂D₄) has been recorded with an unapodized resolution of 0.006 cm⁻¹ in the frequency range 2150 to 2250cm⁻¹. The v₁₁ band, with a band centre of about 2201 cm⁻¹, was found to be perturbed by the nearby v₂ + v₇ band centred at about 2235 cm⁻¹ by a b-type Coriolis interaction. By fitting a total of 772 infrared transitions of v₁₁ using a Watson's A-reduced Hamiltonian in the I^r representation with the inclusion of b-type Coriolis interaction term, two sets of constants, up to quartic distortion constants for the v₁₁ = 1 state, and principal rotational constants for the v₂ + v₇ = 1 dark state, were derived. The inertia defect of the v₁₁ state was found to be 0.0693 ± 0.0004u Ų.