Vinylamine has a double minimum potential. The 0^– tunneling state is 45.18 cm^–1 or 1.35 THz higher in energy than the 0⁺ state. Strong a-type and weak b-type transitions occur within the states while strong c-type transitions are allowed between the states. The lines within the 0⁺ and 0^– states have been summarized by
(1) R. D. Brown, P. D. Godfrey, B. Kleibomer, A. P. Pierlot, and D. McNaughton, 1990, J. Mol. Spectrosc. 142, 195.
Transitions between the states have been described in
(2) D. McNaughton and E. G. Robertson, 1994, J. Mol. Spectrosc. 163, 80.
The authors of (2) have kindly provided transition frequencies with uncertainties from (1) and (2). The parameter set is slightly more extensive than that in (2). The estimated uncertainty of the far-infrared transitions is 0.002 cm^–1 or 60 MHz. This uncertainty is assumed to be largely statistical, however, calibration uncertainties may still be a fair fraction of this value.
The a- and b dipole moment components were determined in (1). The total dipole moment has been evaluated in
(3) H. M. Badawi, 2005, J. Mol. Struct., Theochem 726, 253.
The differences between the calculated total dipole moment and the experimentally determined components suggests the c-component between the states to be of order 1 D, maybe even slightly higher. Since this value is not known accurately and since the transitions between the states occur in very differnt frequency regions, a separate entry is provided for transitions between the tunneling states, see e043508.cat.
Frequency predictions for J > 30 and for K_a > 20 should be viewed with caution. In addition, predictions for frequencies and intensities of some strongly perturbed transitions may be less reliable.