ENERGY TRANSFER OF $OH(A^{2} \Sigma ^{+},v`=1)$ IN FLAME GASES
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Date
1981
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Ohio State University
Abstract
Energy transfer from specific rotational levels (quantum Number $N^{\prime}$;) of $v^{\prime}=1$ of the $A^{2}\Sigma ^{+}$ state of the hydroxyl radical has been studied. The environment is the burnt gases ($\sim 70% N_{2}$) of a $Ch_{4/air}$ flame at $T=1900$ K and atmospheric pressure. A tunable laser populates seven individual levels in the range $N^{\prime}=1$ to 16, and rotationally resolved fluorescence measurement are made with a scanning monochromator. The energy transfer rate is found to decrease with increasing $N^{\prime}$. The rotational population distribution for molecules transferred into $v^{\prime}=0$ is thermal-like ($T\sim 2200 $K) for an initial N `=1,5 and 10 in v `=1 but much hotter ($T\sim3400 $K) for an initial N `=13-16. The ratio of the rate of rotational energy transfer within v `=1, to the quenching rate, decreases rapidly over the range N `=13 to 16, which spans the predissociation limit. A definite propensity for transfer to nearby levels, and for maintaining, spin component ($F_{1} vs F_{2}$), is exhibited during rotational relaxation of the levels of high N`.
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