Structure of the Methylamine Molecule. I. Microwave Spectrum of CD3ND2

Abstract

The spectrum of CD3ND2 has been investigated in the 24 000–36 000 Mc region and about thirty lines have been assigned. The rotational spectrum exhibits a fine structure as a result of internal rotation and inversion. An approximate treatment of these internal motions is formulated and shown to give an excellent fit of the observed spectrum. A treatment of Stark effects and nuclear quadrupole interactions is developed and applied to the CD3ND2 spectrum. The relation to the CH3NH2 spectrum is discussed. Molecular constants of CD3ND2 determined from the spectral analysis are: torsional barrier height H=684.7±2 cm-1; dipole moment components μa=0.265 D, μc=1.299 D, total μ=1.326±0.015 D; N14 quadrupole coupling constants χaa=2.35 Mc, χbb=2.12 Mc, χcc=—4.47 Mc. Structural parameters calculated from data on CD3ND2 and CH3NH2 are: rCH=1.093 A (assumed), ∠HCH=109°28′ (assumed), rCN=1.474 A, rNH=1.011 A, ∠HNH=105°52′, ∠CNH=112°3′; the nitrogen atom is located 0.091 A from the CH3 symmetry axis.