The Rotational Spectrum of the Ground State of Methylamine

Published

February 1, 2005

Author(s)

Vadim V. Ilyushin, E A. Alekseev, S F. Dyubkoa, R A. Motiyenkoa, Jon T. Hougen

Abstract

Recent progress is reported in measuring, assigning and fitting the rotational spectrum of the ground vibrational state of methylamine, CH3NH2, a spectrum complicated both by internal rotation of the methyl top and by inversion of the amino group. New measurements of 513 rotational transitions with J up to 30 and K up to 9 were carried out between 49 and 326 GHz using the millimeter-wave spectrometer in Kharkov. After removing the observed quadrupole hyperfine splittings, these new data along with previously published measurements were fitted to a group-theoretical high-barrier tunneling Hamiltonian from the literature, using 57 parameters to give an overall weighted standard deviation of 0.79 for 850 far-infrared and 668 microwave transitions in the ground state. The root-mean-square deviation of 0.016 MHz obtained for 366 millimeter-wave transitions measured with 0.020 MHz accuracy represents an approximately 30-fold improvement in fitting accuracy over past attempts.

Citation

Journal of Molecular Spectroscopy

Volume

229

Issue

No 2

Pub Type

Journals

Keywords

amino group inversion motion, high-barrier tunneling formalism, least-squares fit, methyl group internal rotation, methylamine, microwave spectrum

Citation

Ilyushin, V. , Alekseev, E. , Dyubkoa, S. , Motiyenkoa, R. and Hougen, J. (2005), The Rotational Spectrum of the Ground State of Methylamine, Journal of Molecular Spectroscopy (Accessed December 19, 2025)