RECOMBINATION DELAYED FLUORESCENCE IN CRYSTALLITES OF SOME ORGANIC MOLECULES
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Date
1971
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Publisher
Ohio State University
Abstract
In view of a certain number of photobiological processes for which it has been suggested that the primary action of light is to cause the ionization of some specific molecules, a systematic study has been carried out in our laboratory on the effect of primary U.V. irradiation on the nature of the delayed emission in some compounds like the aromatic $hydrocarbons^{1}$, the acridine $dyes^{2}$, the xanthene $dyes^{3}$, and the $amines^{4}$. It has been shown that the presence of a very small amount of aggregated solute molceules in an ethanol rigid glass matrix is sufficient to produce a delayed fluorescene (DF) with the following characteristics: 1. Shift in the positions of the vibrational peaks or appearance of new low energy components compared to the normal fluorescence spectra. 2. The action spectra of the DF can be correlated with the treshold for intrinsic charge carrier generation in the crystalline state and generally shows “antibatic” relationship with the absorption spectra of the solute molecules. 3. The DF obeys the relationship ${I}_{DF}\infty I_{o}^{n}$ with n equal to 1.0. 4. The decay with time of the DF generally obeys a double exponential law with time constants varying between 0.3 to 10.0 sec. It has been proposed that the DF originates from electron-hole recombination after the detrapping of charge carriers in the crystallites first generated by the incident U.V. light.
Description
$^{1}$M. Ewald and G. Durocher, J. Chem. Phys., July (1971). $^{2}$M. Ewald, B. Muel and G. Durocher, Chem. Phys. Letters, 5, 83 (1970). $^{3}$M. Ewald and G. Durocher, Chem. Phys. Letters, April (1971). $^{4}$M. Ewald and G. Durocher, to be published.""
Author Institution: D\'{e}partment de Chimie, Universit\'{e} de Montrcal B.P. 6128
Author Institution: D\'{e}partment de Chimie, Universit\'{e} de Montrcal B.P. 6128