A combined fit of HCO⁺, v₂ = 0 and 1, has been performed. It has been altered considerably with respect to the Oct. 2005 entry. The v = 0 transitions frequencies have been summarized largely in
(1) F. Tinti, L. Bizzocchi, C. Degli Esposti, and L. Dore, 2007, Astrophys. J., 669 L113.
Additional high frequency transitions were taken from
(2) V. Lattanzi, A. Walters, B. J. Drouin, and J. C. Pearson, 2007, Astrophys. J., 662, 771.
The uncertainties of these transitions have been increased to 100 kHz because of large residuals compared to predictions from (1); the remainder of the data from that work seems to be judged appropriately or maybe even conservatively. With respect to prediction based on data from (1) only, those from (2) reduce the uncertainties slightly.
The v₂ = 1, J = 4 – 3 transitions were taken from
(3) E. Hirota and Y. Endo, 1988, J. Mol. Spectrosc., 127, 527.
Higher-J transitions were provided by (2).
ν₂ infrared data from
(4) K. Kawaguchi, C. Yamada, S. Saito, and E. Hirota, 1985, J. Chem. Phys. 82, 1750;
as well as from
(5) P. B. Davies and W. J. Rothwell, 1984, J. Chem. Phys. 81, 5239
were also used in the fit.
Predictions beyond 2 THz should be viewed with caution.
The dipole moment is taken from an ab initio calculation by
(6) P. Botschwina, M. Horn, J. Flügge, and S. Seeger, 1993, J. Chem. Soc. Faraday Trans. 89, 2219.
The partition function takes into account both vibrational states; individual contributions are given in parentheses.