Primary Processes in the Photobleaching of Eosin as Revealed by the Flash Technique

Abstract

Abstract Reductive photobleaching of eosin and uranin in ethanol solutions was studied by the flash technique. Transient spectra of semiquinone with a lifetime of millisecond order was established. In addition, another transient spectra with a life of the same order was observed in the case of eosin. This was interpreted to be due to a certain complex intermediate between ethanol and eosin, formed prior to semiquinone. The aerated alcoholic solution and the evacuated aqueous solution, when illuminated by a flash, showed no transient spectra in the wavelength region of the above two intermediates. The fluorescence of the aerated ethanol solution produced by the flash had about twenty times as large intensity as that of the evacuated solution induced under otherwise similar condition. A scheme for the primary processes of the reductive photobleaching involving the above complex can interpret all these results satisfactorily.