The experimental lines are from
(1) S. Bailleux, M. Bogey, C. Demuynck, J.-L. Destombes, and A. Walters, 1994, J. Chem. Phys. 101, 2729.
The reported uncertainties of "better than 50 kHz" appear to be too conservative by far. We have used 20 kHz, which appears to be slightly conservative still. Watson's S-reduction was used here. Since D_K was only slightly determined and rather small compared to an ab initio value, an estiamted value was kept fixed in the fit. Some closely spaced asymmetry doublets show essentially symmetric, fairly large deviations. These lines have been omitted from the fit here. The deviations may be caused by the Stark effect. Unresolved doublets were retained, but those with calculated splitting of more than 1 MHz were not merged. Predictions with uncertainties larger than 0.3 MHz should be viewed with caution. The data set is deemed to be sufficient for observational purposes.
The dipole moment is from an ab initio calculation by
(2) B. Ma and H. F. Schaefer III, 1994, J. Chem. Phys. 101, 2734.
At low temperatures, it may be necessary to discern between ortho-H₂SiO and para-H₂SiO. The ortho and para states are described by K_a being odd and even, respectively. The nuclear spin-weights are 3 and 1 for ortho-H₂SiO and para-H₂SiO, respectively. The J_KaKc = 1₁₁ is the lowest ortho state. It is 6.1173 cm^–1 above ground.
Separate para and ortho predictions are available up to J = 10 and K_a = 3 along with separate para and ortho partition function values. Note: the spin-weight of 3 for the separate ortho predictions has been eliminated.