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Note: The lower energy
conformer of glyoxal is the trans-conformer with
zero dipole moment because of symmetry.
(1) H. Hübner, A. Leeser, A. Burkert, D. A. Ramsey,
and W. Hüttner,
1997, J. Mol. Spectrosc. 184, 221,
determined the cis-conformer to be higher by
1555 ± 48 cm–1
or 2237 ± 69 K. Therefore, its
relative population is very low even at a rotational
temperature of 300 K. The transition frequencies,
their uncertainties, and the dipole moment were
determined in (1).
The predictions should be good enough to search for
the molecule in space. Transitions with predicted
uncertainties of 0.3 MHz or larger should be viewed
with great caution.
Note: the energies
and intensities do not include the conformational
energy. And the partition function only considers the
ground vibrational state of the cis-conformer.
Spin-statistics matter for the intensities.
Ortho and para states are described by
Ka + Kc being
odd and even, and the spin-weight ratio is
3 : 1.
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