FLUORESCENCE OF $SO_{2}$ FROM EXCITATION IN THE 3200-3300 \AA REGION
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Date
1976
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Ohio State University
Abstract
A frequency doubled narrow band ($0.1 cm^{-1})$ dye laser has been used to excite $SO_{2}$ fluorescence in the previously unexplored 3200-3350 {\AA} region of absorption. This encompasses several bands in the $^{1}A_{2} - ^{1}A_{1} (\Pi^{*} - \Pi)$ system recently rotationally analyzed by Hamada and $Merer.^{1,2}$ Several observations have been made. 1) At all excitation wavelengths biexponential decay of fluorescence from the $^{1}A_{2}$ and $^{1}B_{1}$ states results. Hamada and Merer have proposed that the origin of $^{1}B_{1}$ state is near 3100 {\AA}. Although our observation does not rule out their proposal it mitigates against it. 2) At all wavelengths, $\lambda \leq 3350$ {\AA} studied, the absorption (resolution $0.1 cm^{-1}$) in the $^{1}B_{1}$ state appears to be continuous. The efficiency of excitation of $^{1}B_{1}$ state is still quite large even at 3350 \AA. 3) For some of the $^{1}A_{2} {\leftarrow} ^{1}A_{1}$ vibronic bands (3226, 3268, and 3274 \AA) we find very different behavior. Excitation in these bands leads almost entirely to near single exponential decay characteristic of the $^{1}A_{2}$ state. This is in marked contrast to previous reports in the elements letter band $region.^{3}$ 4) We were unable to study the longer wavelength bands reported by Hamada and Merer near 3340, and 3393 \AA. Absorption at these wavelengths was so dominated by the pseudocontinuous transition to the $^{1}B_{1}$ state that $^{1}A_{2}$ absorptions were undetectable.
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Author Institution: Department of Chemistry, University of Maryland; Department of Chemistry, Naval Research Laboratory