Reactions between excited dyes and reagents in active media of bleaching-wave lasers

Alcohol molecules enhanced the lasing efficiency of ether solutions of coumarins C47 and C102 and substantially slowed down the bleaching reactions between coumarins and stilbene in solutions. The dependences of the influence of alcohol molecules on the bleaching reactions, efficiency, quantum efficiency, and fluorescence band shift of these coumarins indicated an exciplex reaction mechanism. The rate constants of exciplex formation were estimated. It was proposed to use the shift of the fluorescence spectra of coumarins in ether with added alcohol to estimate the rates of their reactions with stilbene when making a preliminary selection of dyes for bleaching-wave lasers. Similarly, dimethyl sulfoxide molecules slowed down the bleaching reaction of coumarins with 1,4-diphenylbutadiene (DPB). The shift of the fluorescence spectrum of coumarin in dimethylsulfoxide was correlated with the rate of its reaction with DPB. The feasibility of appreciable blocking of bleaching reactions by impurities, present in solutions in concentrations of fractions of a percent, imposed additional requirements on the monitoring of the chemical purity of active media and solvents used in bleaching-wave lasers.