The experimental frequencies have been reported by
(1) S. Blanco, J. C. Lopez, A. Lessari, and J. L. Alonso, 2006, J. Am. Chem. Soc. 128, 12111;
and by
(2) A. V. Kryvda, V. G. Gerasimov, S. F. Dyubko, E. A. Alekseev, R. A. Motiyenko, 2009, J. Mol. Spectrosc. 254, 28.
Additional microwave transitions were also considered. These were taken from
(3) M. Stubgaard, PhD thesis, 1978, Københavns Universitet.
Claus Nielsen and Matt Johnson are thanked for providing the data from (3). The supplementary material to (2) also contained unpublished lines from previous studies in that laboratory. These data fit nicely to 100 kHz. One of the four transitions of (1) (below 9 GHz) was omitted from the fit because of residuals much larger than the uncertainties.
Apr. 2013: The data from (3) have been merged.
Several higher order distortion terms have been estimated.
Predictions with uncertainties larger than 0.3 MHz should be viewed with caution. It is conceivable that the predictions are accurate enough for astronomical observations.
Vibrational contributions to the partition function will be provided.
The dipole moment was assumed to agree with that of the main isotopolog, which was determined by
(4) R. J. Kurland and E. B. Wilson, 1957, J. Chem. Phys. 27, 585.