RELATIONSHIP BETWEEN ABSORPTION INTENSITY AND FLUORESCENCE LIFETIME OF MOLECULES
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Date
1962
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Ohio State University
Abstract
The equation usually given relating fluorescence lifetime to absorption intensity is strictly applicable only to atomic transitions. For strong transitions in molecules, a slightly modified equation should be valid: $$1/\tau_{0}=2.880 \times 10^{-9}n^{2}< \nu_{1}^{-3}>^{-1}_{av}(g_{1}/g_{u})\int edln_{v}$$ where n is the refractive index of the medium, $g_{t}$ and $g_{u}$ are the degeneracies of the lower and upper states, and $\bar{\nu}$ is the frequency in $cm^{-1} (\nu_{1}$ refers to the fluorescence spectrum). $\tau_{u}$ would be the mean lifetime in the absence of competing processes. The integration is over the electronic absorption band in question. Fluorescence lifetimes of a number of organic molecules in solution have been measured using a phase fluorometer. The results have been compared with lifetimes calculated using the above formula. In most cases the agreement is within experimental error, indicating that the equation is valid for such transitions.
Description
$^{\ast}$Present address: Dept. of Chemistry. Rice University, Houston I. Texas. $^{\dagger}$ Present address: Dept. of Chemistry. Harvard University, Cambridge, Mass.
Author Institution: Department of Chemistry and Lawrence Radiation Laboratory, University of California
Author Institution: Department of Chemistry and Lawrence Radiation Laboratory, University of California