I-Resonance Perturbation of IR Intensities in 12C2H2 near 13.7 μm

Abstract Using TDL and FT spectrometric data at 0.0005 and 0.0025 cm −1 spectral resolution, respectively, individual line intensities of the ν 5 fundamental and the seven strongest hot bands, ν 4 + ν 5 ← ν 4 and 2ν 5 ← ν 5 , of 12 C 2 H 2 in the 13.7-μm region have been measured. Except for the 2ν 2 f 5 ← ν 1 f 5 hot band, strong intensity perturbation due to l -type doubling and resonances have been quantitatively determined for all hot bands. The zeroth-order vibrational dipole moment derivative for the ν 5 bending mode is identical within 10% for all bands observed. Since an extra factor of 1 2 appears in the square vibrational transition moment for the combination band, its intensity is reduced by half and is comparable in magnitude to the 2ν 5 ← ν 5 hot bands. For the ν 5 fundamental a square dipole moment derivative of Γ 2 v = 0.09069(24)D 2 has been determined.