The entry is based on a line list file provided by L.H. Xu
from the review
(1) L.H. Xu and F. J. Lovas,
1997, J. Phys. Chem. Ref. Data 26, 17.
Details on the RAM (RHO axis method)
and fitting program employed to reduce the data is available in
(2) L.H. Xu, M. S. Walsh, and R. M. Lees,
1996, J. Mol. Spectrosc. 179, 269
and references therein.
These two papers also give details on the extensive data sets
considered in the fits. Because of the internal rotation (torsion),
torsionrotation interaction, and large effects
of centrifugal distortion, global modeling of the
methanol spectrum is a challenging task.
Nevertheless, restricting the data set to v_{t} = 0, 1,
J_{max} = 20, and K_{max} = 14,
the input data was reproduced within experimental uncertainties.
Very small experimental uncertainties have been set to 50 kHz
for most of the microwave lines in the fit.
Certain prediction, in particular those of higher J,
may be found outside three times the uncertainties.
However, because of the large body of transitions observed by
FTFIR spectroscopy, it is expected that these deviations are
within 6 MHz, an uncertainty value assigned to the FTFIR data).
Note: Currently the base 10 logarithm of
S_{g} μ_{g}^{2},
which is temperature independent, is given instead of
the base 10 logarithm of the intensity at 300 K !
The quantum numbers given are those of (1) and (2),
but slightly rearranged for layout reasons. They are
J, (sign)K_{a}, K_{c},
(parity), immediately followed by v_{t}.
The parities + and – refer to A+ and A – states;
while states with no parity designation refer to E symmetry.
A signed value of K_{a} is used to differentiate
(+)E_{1} from (–)E_{2} states.
It should be emphasized that E_{1} and E_{2}
states belong to the same E symmetry species.
As usual, the energies in the catalog entry are given with respect to
the lowest rotational level (0_{00} of the
v_{t} = 0, A state) which is defined as zero.
The energies given in the documentation refer to the 0_{00} rotational levels of the
v_{t} = 0, A and E states and the
v_{t} = 1, E and A states, respectively.
The dipole moment is assumed to be the same as for
the main isotopmer, see e032504.cat.
Note: The current entry takes
into account contributions of the permanent dipole moment
only ! Torsional or rotational dependences as well as
changes in the dipole moment with torsional state have not yet been
determined – or only to an insufficient amount. The effects of
these contributions may be nonnegligible in certain instances.
