A vibration-rotation band of monodeuteromethane

Abstract

The fundamental vibration band of monodeuteromethane near 4$\cdot $5$\mu $, connected with the stretching of the C$\chembond{1,0} $D bond, has been reinvestigated with very high dispersion. It provides a good example of well-resolved parallel-type band structure of a symmetric top molecule in which the K splitting of P and R lines is clearly seen. Alternations of intensity are also found in accordance with the nuclear spin of the three hydrogen atoms. The rotational constants B$_{0}$ and B$_{1}$ have been determined, giving r$_{0}$(C$\chembond{1,0} $H) = 1$\cdot $0924 angstrom. The centrifugal stretching coefficient D$_{J}$ and its variation in the different vibrational states have also been measured. Analysis of the K splitting of the R and P lines reveals an anomaly between the sets on the two sides of the band origin, which seems to suggest that some unforeseen molecular interaction is neglected in the method at present accepted for calculating the molecular rotational energy levels.