Effect of Centrifugal Distortion on the Shape of the Hydrogen Sulfide Fundamental Infrared Bands

Abstract

The fundamental infrared vibration bands of hydrogen sulfide exhibit an interesting intensity anomaly characterized by P branches which are much weaker than the corresponding R branches. This work shows that this anomaly is caused by centrifugal distortion of the nonrigid molecule. A formalism based on a semi‐classical approach is used to calculate the vibration—rotational line positions and their intensities. The computed theoretical spectra are in good agreement with the experimental spectra. This formalism also gives a method of determining the relative sign of (∂μ/∂Q) with respect to μ₀. The values of (∂μ/∂Q) needed in the calculations were obtained from the experimental integrated band intensities and were found to be (∂μ/∂Q₁) = −4.4 esu g^−½ and (∂μ/∂Q₂) = +8.7 esu g^−½.