The entry is based on a combined fit of field free data of OH⁺, OD⁺, and ¹⁸OH⁺. The N = 2 – 1 transition frequencies of OD⁺ were taken from
(1) P. Verhoeve, J. P. Bekooy, W. L. Meerts, J. J. ter Meulen, and A. Dymanus, 1986, Chem. Phys. Lett. 125, 286.
Infared transitions of ¹⁸OH⁺ with N" between 0 and 10 were taken from
(2) M. Gruebele, E. Keim, A. Stein, and R. J. Saykally, 1988, J. Mol. Spectrosc. 131, 343.
Details of the OH⁺ fit have been published in
(3) H. S. P. Müller, F. Schlöder, J. Stutzki, and G. Winnewisser, 2005, J. Mol. Struct. 742, 215.
The N = 1 – 0 transition frequencies were taken from
(4) J. P. Bekooy, P. Verhoeve, W. L. Meerts, and A. Dymanus, 1985, J. Chem. Phys. 82, 3868.
The N = 13 – 12 transition was reported in
(5) D.-L. Liu, W.-C. Ho, and T. Oka, 1987, J. Chem. Phys. 87, 2442.
Vibration-rotation transitions up to v = 5 – 4 were also included in the fit. These were published in
(6) B. D. Rehfuss, M.-F. Jagod, L.-W. Xu, and T. Oka, 1992, J. Mol. Spectrosc. 151, 59.
The N = 1 – 0 transition may well be the only one observable in space. It is conceivable that the predictions of its frequencies are sufficiently accurate for astronomical purposes. The uncertainties of the strong J = 2 – 1 component near 515.5 GHz are probably somewhat small. Predictions at higher quantum numbers should be viewed with some caution.
The dipole moment was assumed to agree with that of the main isotopolog, see e017501.cat.