MOLECULAR CONSTANTS OF SO IN THE $^{1}\Delta$ STATE BY A COMBINED USE OF GAS PHASE EPR AND MICROWAVE ROTATIONAL SPECTRA
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Date
1970
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Ohio State University
Abstract
The rotational transition $J=3\leftarrow 2$ of SO in the a $^{1}\Delta$ state has been detected at $127770.45\pm 0.15$ MHz with microwave spectroscopy. This is the first observation of microwave rotational transition for a molecule in an electronically excited state. The rotational constant was found to be $B_{o}=21295.1 \pm 0.7$ MHz and the dipole moment obtained was $1.336 \pm 0.045$ D. Gas-phase EPR spectroscopy at 4460 MHz in the C-band region has revealed five lines of the six allowed transitions for the rotationally excited J = 3 level of SO in the $^{1}\Delta$ state besides four lines for the J = 2 ground level. The use of the C band in place of the X band (ca. 9 GHz) conventionally employed doubles the measurable resonance region and hence enables one to determine molecular constants more precisely. The analysis of the EPR spectra has resulted in the l-uncoupling constant $\Sigma_{\Pi}<\Delta|B_{o}L_{x}|\Pi><\Pi|L_{x}|\Delta>/(E_{\Pi}-E_{\Delta}) =0.60 \pm 0.11\times 10^{-4}$, using the theoretical values of $g_{L} = 1,00000$ and $g_{z}^{N} = -0.00027$, as well as the rotational constant $B_{o}$ determined above, and assuming finite perturbations only from the $^{1}\Pi$ states. If only one $^{1}\Pi$ state contributes dominantly to the perturbation, the perturbing state lies $12000 cm^{-1}$ above the $^{1}\Delta$ state under pure precession hypothesis.
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Author Institution: Sagami Chemical Research Center