Article ID | Journal | Published Year | Pages | File Type |
---|---|---|---|---|
9589584 | Journal of Molecular Spectroscopy | 2005 | 18 Pages |
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 326Â 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 53 parameters to give an overall weighted standard deviation of 0.80 for 850 far-infrared and 673 microwave transitions in the ground state. The root-mean-square deviation of 0.018Â MHz obtained for 346Â millimeter-wave transitions measured with 0.020Â MHz uncertainty represents an approximately 30-fold improvement in fitting accuracy over past attempts.
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Authors
V.V. Ilyushin, E.A. Alekseev, S.F. Dyubko, R.A. Motiyenko, J.T. Hougen,