The 240 nm band system of methylamine: a preliminary analysis of the rotational structure of the 0–0 band of CH3ND2

The ultraviolet absorption spectrum of CH3ND2 has been observed in the 231–242 nm (43 300–41 300 cm−1) region with 10 m Eagle and 7.3 m Ebert vacuum spectrographs. An analysis has been made of the rotational structure in the 238.1–236.7 nm (42 000–42 240 cm−1) region. It has been shown that, in the excited electronic state, the methyl group is rotating freely with respect to the amino group around the C—N bond as axis. Here the moment of inertia of the methyl group was found to be 3.4054 A2 amu around the molecular axis, and that of the deuterated amino group ND2 3.4081 A2 amu. The sum 6.8135 A2 amu is appreciably greater than IA = 6.6280 A2 amu, the moment of inertia for the overall rotation of the molecule.