Excition dynamics in the J-aggregates of a carbocyanine dye

We report on the exciton dynamics in the J-aggregating dye 5,5', 6,6'-tetrachloro-1,1'-diethyl-3,3'-di(4-sulfobutyl)-benzimidazolocarbocyanine which is known readily to form J-aggregates, even at room temperature and at a low concentration. We performed a series of time-correlated singlephoton-counting experiments at different emission wavelengths and at different temperatures in the range between 1.5 and 125 K. Additionally, the temperature dependence of the relative fluorescence quantum yield was determined.