The Infrared Absorption Spectrum of Methyl Deuteride

Abstract

The six fundamental vibrational frequencies of methyl deuteride were observed and the fine structure of the bands resolved. The frequencies are v6 = 1156.3, v5 = 1306.8, v4 = 1477.1, v3 = 2205.25, v1 = 2983.0, v2 = 3031.0. From the fine structure of the bands, the moments of inertia are found to be IA=7.166×10−40 g cm2,IC=5.298×10−40 g cm2and the internuclear distances are C–H=1.093×10−8 cm, H–H=1.785×10−8 cm.From the four previously known frequencies of methane and each of the frequencies of this molecule, the values of the five potential constants are computed. Three of the sets are consistent and agree well with the values found by Dennison and Johnston, but the other three sets have either negative or imaginary values. The frequencies from which these are calculated are the ones which take part in a resonance interaction which was not included in the theory. From the observed spacings of the zero branches of the perpendicular bands, extreme ranges of the rotation-vibration interaction factors are computed. An overtone, 2v4 = 2923, was also observed as were three frequencies of the molecule CH2D2, at 1036.0, 1090.5, and 1235.5 cm—1.