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 predictions should be viewed with caution throughout, even more so as the predicted uncertainties are somewhat optimistic. Uncertainties in the fine structure splitting are probably most important for the N = 1 – 0 transition.
The dipole moment was assumed to agree with that of the main isotopolog, see e017501.cat.