According to ab initio calculations, thioxyhydroxymethylium is considerably higher in energy than its oxythiohydroxymethylium isomer. The three lowest K_a = 0 transitions were reported by
(1) Y. Ohshima and Y. Endo, 1996, Chem. Phys. Lett. 256, 635.
Information on additional low order spectroscopic parameters were taken from an infrared study by
(2) T. Nakanaga and T. Amano, 1987, Mol. Phys. 61, 313.
However, in the absence of transition frequencies or ground state combination differences, the reliability of predictions for transions with K_a ≥ 1 can not be evalutated. Therefore, predictions are limited to K_a = 0. However, the partition function takes into account higher K_a levels. Judged by the rms error of the fit, the experimental uncertainties from (1) may be rather conservative. But with two parameters determined from three transition frequencies, this remains uncertain for now. Predictions beyond 100 GHz should be viewed with caution.
The dipole moment component is from an ab initio by
(3) S. E. Wheeler, Y. Yamaguchi, and H. F. Schaefer III, 2006, J. Chem. Phys. 124, Art. No. 044322.