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The dibridged Si2H2 is the lowest
energy isomer.
The experimental lines are from
(1) M. Bogey, H. Bolvin, M. Cordonnier, C. Demuynck,
J.-L. Destombes, and A. G. Császár,
1994, J. Chem. Phys. 100, 8614.
The reported uncertainties of "better than 50 kHz"
appear to be too conservative by far. We have used
20 kHz, which appears to be appropriate.
Watson's S-reduction was used here. Should molecules
with two Si atoms exist in circumstellar envelopes
of late-type stars, then probably in the outer, cooler
regions. Therefore, the predictions should be sufficient
for astronomical observations.
Predictions with uncertainties larger than
0.3 MHz should be viewed with caution.
The dipole moment is from an ab initio calculation
by
(2) H. S. P. Müller and D. E. Woon,
2013, J. Phys. Chem. A 117, 13868.
At low temperatures, it may be necessary to discern between
ortho-H2SiO and para-H2SiO.
The ortho and para states are described by
Kc being odd and even, respectively.
The nuclear spin-weights are 3 and 1 for
ortho-Si2H2 and
para-Si2H2, respectively.
The JKaKc =
101 is the lowest ortho state.
It is 0.4830 cm–1 above ground.
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