Aug. 2022: The calculated intensities were wrong for an unknown reason. The error was corrected.
The range of excited states was extended with respect to the initial entry from Feb. 2007. The version number was retained. A global fit of data for all isotopic species and the experimental lines were summarized in
(1) H. S. P. Müller, M. C. McCarthy, L. Bizzocchi, H. Gupta, S. Esser, H. Lichau, M. Caris, F. Lewen, J. Hahn, C. Degli Esposti, S. Schlemmer, and P. Thaddeus, 2007, Chem. Phys. Phys. Chem., 9, 1579.
The newly recorded transitions extend to almost 1 THz and to high vibrational states. Previous pure rotational data from
(2) E. Tiemann, E. Renwanz, J. Hoeft, and T. Törring, 1972, Z. Naturforsch. 27a, 1566;
and from
(3) M. E. Sanz, M. C. McCarthy, and P. Thaddeus, 2003, J. Chem. Phys., 119, 11715; as well as rovibrational data from
(4) C. I. Frum, R. Engleman, Jr., and P. F. Bernath, 1990, J. Chem. Phys., 93, 5457;
and from
(5) H. Birk and H. Jones, 1972, Chem. Phys. Lett. 175, 536
were also used in the fit.
The predictions should be adequate up to about 2 THz.
The dipole moment for the v = 0 is an average value from
(6) J. Hoeft, F. J. Lovas, E. Tiemann, and T. Törring, 1969, Z. Naturforsch. 24a, 1422;
and from
(7) A. N. Murty and R. F. Curl, Jr., 1969, J. Mol. Spectrosc., 30, 102.
The two values agree to 0.01 D, but the uncertainties are more than five times as large. Note: ab initio calculations suggest that the dipole moment decreases by about one percent or somewhat less upon excitation of one quantum of vibration. Centrifugal distortion effects decrease the intensity by about one to two percent near J of 50 near 1 THz.
Vibrational states v ≤ 35 have been considered for the calculation of the partition function.