ON THE HIGH PRESSURE CARBON BANDS
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Date
1968
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Ohio State University
Abstract
High Pressure Carbon bands from a $v""$-progression of the $^{2}II-^{2}II$ system of $C_{2}$ with the lower $^{2}II$ as the common final state, $X^{1} {^{2}}II_{***}$ of the Swan bands. The initial $^{2}II$ state was suggested to be the same as that of the Swan system with $v^{\prime} = 6$. The fact that the high pressure carbon bands could be excited quite intensely almost to the exclusion of Swan bands under certain conditions of discharge was explained as an inverse predissociation of the initial $^{2}II$ state of Swan bands at $v^{\prime} = 6$. This explanation for the selective excitation of the high pressure bands was found untenable as the true dissociation energy of $C_{2}$ was known to be much higher than that would correspond to $v^{\prime} = 6$ of $A^{3}II_{***}$ state. A detailed investigation of these bands is undertaken in order to identify the initial level of the high pressure carbon bands. The bands have been excited in condensed discharges through CO containing about 40 percent enriched $^{13}C$ and photographed under high resolution. Rotational structure analysis and isotope shifts of the bands support the suggestion that they are part of the Swan system with $v^{\prime} = 6$. Rotational levels with $N = 19, 21$ and 23 of $v^{\prime} = 6$ level of the $A^{3}II_{***}$ state are found to be perturbed by corresponding levels of the $A^{***}\Sigma^{-}_{g}$ state. Results of these studies are discussed.
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Author Institution: Head, Spectroscopy Division, Bhabha Atomic Research Centre