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The Rotational Spectrum of the Ground State of Methylamine



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


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.
Journal of Molecular Spectroscopy
No 2


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


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 April 15, 2024)
Created January 31, 2005, Updated October 12, 2021