The microwave spectrum of methyl isocyanate, CH3NCO, has been measured in the range from 8 to 40 GHz. More than 200 lines have been assigned to the a-type J + 1 ← J rotational transitions (J = 0 to 3) arising from molecules in the ground state and excited torsional and CNC bending states. The observed spectrum has been analyzed and successfully interpreted in terms of the five-dimensional quasi-symmetric top molecule model accounting explicitly for the large-amplitude CNC bending motion, and internal and overall rotation. In the least-squares fitting to the observed transition energies the values of the parameters of the CNC bending-torsional potential function have been determined. © 1986.
Koput, J. (1986). The microwave spectrum of methyl isocyanate. Journal of Molecular Spectroscopy, 115(1), 131–146. https://doi.org/10.1016/0022-2852(86)90281-X