A global fit of data for all isotopic species and the experimental lines have been 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 transition dipole moment ia an estimate from
(6) A. Lopez Piñeiro, R. H. Tipping, and C. Chackerian, 1987, J. Mol. Spectrosc. 125, 184.
Vibrational states v ≤ 10 have been considered for the calculation of the partition function. Contributions of the individual vibrations are given in parentheses for v ≤ 5.