Chemistry Faculty Research


Contrasting Patterns of Coupling between the CH Stretches and the Large-Amplitude Motions in the Molecules, CH3NH2, CH3OH2+ and CH3CH2radical Dot

Document Type


Publication Date

Spring 3-16-2015


In each of the title molecules, torsional and inversion tunneling occurs between six equivalent minima. The coupling between these large-amplitude motions and the CH stretch vibrations stems from the variation of the CH stretching force constants as a function of the torsional and inversion coordinates. First principles 2D maps of the variation of the CH-stretch force constants are reported. Although the torsional barriers differ by more than a factor of 20, the torsion–inversion–vibration coupling is similar for two of the species, CH3NH2 and CH3CH2, but is much weaker and qualitatively different in form for the third species, CH3OH2+.

Publication Title

Chemical Physics Letters



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