Photophysics of rigidized 7-aminocoumarin laser dyes

摘要

An unusual slow rise of fluorescence intensity from Coumarins 102, 314, and 334, observed under conditions of high intensity laser excitation prompted further investigation of their photophysics by photoquenching, time-resolved transient absorption spectroscopy and time-resolved amplified stimulated emission. The slow rise was found to be the consequence of multi- photon excitation. Principal fate of coumarin molecules so excited was shown to be intersystem crossing to the nonemissive triplet manifold. Rate of intersystem crossing was estimated as ca. 10$+10$/ s$+$MIN@1$/; energy matching between a higher excited singlet state, S$-n$/, and a higher triplet, T$-n$/, is implicated.