Annabel A. Muenter

Singlet exciton annihilation in the picosecond fluorescence decay of 1, 1'-diethyl-2,2'-cyanine chloride dye j-aggregate☆

Abstract Time-resolved fluorescence decay of the J-aggregate of the title dye has been measured with a jitter-free picosecond streak camera and by time-correlated single photon counting. The observed decay is sensitive to the excitation intensity, and the dependence can be simulated by a model involving singlet-singlet exciton annihilation at high exciton densities. The estimate of exciton mobility from this exciton annihilation experiment is similar to results from fluorescence quenching experiments.

Origin of low-temperature delayed fluorescence in cyanine dyes

Abstract The delayed fluorescence found in rigid-glass solutions of cyanine dyes is shown to result from the presence of trace quantities of phosphorescent impurities and not from a low-energy photoionization process, as previously suggested. For quinoline cyanine dyes, the predominant impurities are identified as quinolones, highly phosphorescent compounds formed by oxidative degradation of the dyes.

New approach to silver halide photography using radical cation chemistry

A new mechanism for spectral sensitization of silver halide is described, which can potentially double the sensitivity of photographic emulsions. The photooxidized sensitizing dye is trapped using an organic donor molecule, which fragments to form a cation and a reducing radical, which injects an electron into the conduction band of the silver halide. In this way, two conduction-band electrons can be produced for each absorbed photon.