Participation of singlet oxygen in photodegradation of air-saturated solutions of coumarin dyes

Abstract

Solutions of coumarin dyes are used to generate stimulated emission in the blue-green region of the spectrum [i]. During irradiation of the active medium by flash pump lamps, the dye becomes degraded~ and this leads to a decrease in the generation energy. The photolysis ofcoumarin dyes has been studied by several authors [2-6]. At present, the photodimerization reaction of coumarins in solutions [2] and photoreduction in deoxygenated ethanol [3] are known, and the opening of the pyrone ring of coumarins by the action of irradiation is suggested in some papers [4, 5]. Dealkylation products of amino groups and oxidation products of the methyl group were isolated as the photolysis products of 7-diethylamino-4methylcoumarin. It was shown that it is oxidation of the methyl group that determines deterioration in the generational characteristics of the laser, since the photoproducts formed absorb emission in the generation region, while the role of the remaining processes is inappreciable [6]. The oxidation mechanism was not studied. To clarify the oxidation mechanism of the photooxidation of coumarin dyes serving as laser media, we studied the regularities of their photolysis in air-saturated solutions.