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 4.04 ± 0.08 × 107cm−2 · (moles/cc) −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.