Time-resolved excited state dynamics of a cyanine dye

The photophysics and isomerization dynamics in the excited state of a cyani ne dye, 3,3'-di(3-sulfopropyl)-thiacyanine triethylaminium salt was investi gated. Using the femotosecond time-resolved fluorescence up-conversion. tec hnique, wavelength-dependent fluorescence dynamics was observed and the the oretical prediction of the dual fluorescence behavior was vindicated. The r esults were explained using a barrierless isomerization reaction model. The origins of two decay components were assigned to the relaxation within the excited state and the S-1 --> S-0 transition, respectively, and the time c onstants were obtained. (C) 1998 Elsevier Science B.V. All rights reserved.