Laser flash photolysis studies of some rhodamine dyes Characterisation of the lowest excited singlet state of Rhodamine 3B, Sulforhodamine B and Sulforhodamine 101

Abstract

The UV–VIS absorptive and emissive properties of three laser dyes, viz Rhodamine 3B, Sulforhodamine B and Sulforhodamine 101, have been studied in ethanol. Time-resolved methods were used to study the decay of the first excited singlet state of each dye. The absorptive properties of the lowest excited singlet states of the dyes were generated using picosecond laser pulses. Values for the absorption coefficient for the S_n←S₁ absorption process were measured, for each dye, by both comparative and complete-depletion methods. Values for the S₄←S₁ absorption process, in ethanol, were found to be 4.6×10⁴ (444 nm), 3.4×10⁴ (446 nm) and 3.6×10⁴ (458 nm) d mol^-1 cm^-1 for Rhodamine 3B, Sulforhodamine B and Sulforhodamine 101, respectively, with the corresponding values for the S₃←S₁ absorption process being measured as 1.0×10⁵ (556 nm), 1.2×10⁵ (556 nm) and 1.2×10⁵ (578 nm) d mol^-1 cm^-1. The relevance of such data in predicting lasing characteristics of dyes is discussed.