Temperature Dependence of the Spectral Intensity of the Fermi Resonant 1943 cm−1 Band of Carbonyl Fluoride

The temperature dependence of the spectral and integrated intensity of the 1943 cm⁻¹ infrared band of carbonyl fluoride was experimentally determined in the temperature range 300–600°K. The total integrated intensity, α₁₉₄₃, is independent of temperature and has a value of ${\text{4.04 ± 0.08 × 10}}^7{\mathrm{cm}}^{\text{−2}}\mathrm{·\; (}\mathrm{moles}/\mathrm{cc}{)}^{\text{−1}}$ . An expression for the temperature dependence of the theoretical band shape of the ν₂ fundamental vibration of carbonyl fluoride is presented, and numerical results based on this model are compared to the experimental data. Since the first overtone of the ν₁ vibration is in Fermi resonance with the ν₂ vibration, the temperature dependence of the Fermi resonant contribution was evaluated. The Fermi resonance effects were combined with the theoretical band shape to predict the spectral intensity of the 1943 cm⁻¹ band at temperatures above 600°K.