The entry is based on
(1) J. Fisher, G. Paciga, L.H. Xu, S.B. Zhao,
G. Moruzzi, and R. M. Lees,
2007, J. Mol. Spectrosc. 245, 7.
About 550 rotational transition frequencies with
microwave accuracy were taken from
(2) R. H. Hughes, W. E. Good, and D. K. Coles,
1951, Phys. Rev. 84, 418;
from
(3) M. C. L. Gerry, R. M. Lees, and G. Winnewisser,
1976, J. Mol. Spectrosc. 61, 231;
from
(4) Y. Hoshino, M. Ohishi, K. Akabane, T. Ukai,
S. Tsunekawa, and K.Takagi,
1996, Astrophys. J. Suppl. Ser. 104, 317;
from
(5) A. PredoiCross, R. M. Lees, H. Lichau,
M. Winnewisser, and J. R. Drummond,
1997, Int. J. Infrared Millimeter Waves, 18, 2047;
and from
(6) M. Ikeda, Y.B. Duan, S. Tsunekawa, and K. Takagi,
1998, Astrophys. J. Suppl. Ser. 117, 248.
The input data included more than 17000 transitions from (1)
based on Ritz analysis of Fourier transform farinfrared spectra
in the 15–470 cm^{–1} region.
The global analysis covered the v_{t} ≤ 2
torsional states, J_{max} = 30, and
K_{max} = 15 quantum number ranges.
With incorporation of 79 adjustable parameters, the global fit achieved
convergence with an overall weighted standard deviation of 1.072,
essentially to within the assigned measurement uncertainties of
±50 kHz for almost all of the microwave and millimeterwave
lines and ±6 MHz (0.0002 cm^{–1}) to
±15 MHz (0.0005 cm^{–1}) for the
Fouriertransform farinfrared measurements.
Based on the global fit results, this database has been compiled
containing transition frequencies, quantum numbers, lower state
energies and transition strengths (Sμ^{2},
converted here to intensities at 300 K as usual), covering
v_{t} ≤ 2, K_{max} = 15,
and J_{max} = 40 (10 J extrapolation).
Along with the calculated transition frequencies, modeldependent
uncertainties were also determined from the variancecovariance matrix
of the least squares analyses, as usual. Transitions with
predicted uncertainties larger than 0.5 MHz should be
viewed with some caution, those with uncertainties larger than
5 MHz should be great caution.
State numbers 0, 3, and 6 refer to lines with A symmetry
with v_{t} = 0, 1, and 2; state numbers
1, 4, and 7 refer to lines with E symmetry with
K_{a} ≤ 0 and with
v_{t} = 0, 1, and 2; state numbers
2, 5, and 8 refer to lines with E symmetry with
K_{a} > 0 and with
v_{t} = 0, 1, and 2.
Lower state energies are given referenced to the J =
K = 0, A, v_{t} = 0 level,
which is about 127 cm^{–1} above the bottom of
the torsional potential well.
The partition function consider states with v_{t} ≤ 3,
J ≤ 44, and K ≤ 20. The K
levels are sufficient well beyond 300 K, the vibrational and
J levels are about sufficient at 300 K.
Experimental microwave and millimeterwave transition frequencies
have not been merged, but are available in a
line file.
The experimental dipole moment in several torsional states was
reported by
(7) K. V. L. N. Sastry, I. Mukhopadhyay, P. K. Gupta, and J. VanderLinde,
1996, J. Mol. Spectrosc. 176, 38.
