|
The heavy atoms of oxetane are effectively planar, i.e.,
the molecule has a double minimum potential, but the
ground vibrational state is slightly above the barrier.
This leads to a very low-lying, very anharmonic ring
puckering vibration.
The experimental data were taken from
(1) R. A. Creswell, I. M. Mills,
1974, J. Mol. Spectrosc. 52, 392;
and from
(2) A. Lessari, S. Blanco, and J. C. López,
1995, J. Mol. Struct. 354, 237.
Two lines from (1) with residuals much larger than the
uncertainties were omitted from the fit.
The predictions are deemed to be sufficient for all
needs of astronomers. Predictions with uncertainties
larger than 0.3 MHz should be viewed with
caution.
Spin-statistics matter for the intensities.
The nuclear spin-weight ratio is 9 : 7
for ortho-c-C5H5N
: para-c-C5H5N.
The ortho states are described by
Ka odd, the para
states by Ka even.
The dipole moment was taken from (2).
|