The combined fit of several vibrational states has been described in
(1) S. Thorwirth, P. Theulé, C. A. Gottlieb, H. S. P. Müller, M. C. McCarthy, and P. Thaddeus, 2006, J. Mol. Struct. 795, 219.
The majority of the lines was taken from that publication. Additional transitions were taken from
(2) D. J. Meschi and R. J. Myers, 1959, J. Mol. Spectrosc. 3, 405; from
(3) R. L. Cook, G. Winnewisser, and D. C. Lindsey, 1973, J. Mol. Spectrosc. 46, 276; and from
(3) E. Tiemann, J. Hoeft, F. J. Lovas, and D. R. Johnson, 1974, J. Chem. Phys. 60, 5000.
The partition function does take into account vibrational contributions from the first six vibrational excited states ! The ground state values are given in parentheses.
Predictions should be reliable as long as the predicted uncertainties do not exceed 0.5 MHz.
The dipole moment was published in (2).