Photochemistry of Coumarin laser dyes: the role of singlet oxygen in the photo-oxidation of Coumarin 311

Coumarin 311 was shown to sensitize the formation of singlet oxygen, a reactive intermediate proposed to be responsible for degradation of coumarin dyes in dye lasers. The reactivity of Coumarin 311 and various oxidized states of Coumarin 311 with both the 1Δ and 1Σ states of molecular oxygen was determined. Both singlet states of oxygen react predominantly at the dimethylamino substituent. Although singlet oxygen is formed in coumarin dye lasers and oxidizes the dyes, the products resulting from singlet-oxygen oxidation do not interfere with stimulated emission.