Ultrafast excited states relaxation dynamics in solution investigated by stimulated emission from a styryl dye

Ultrafast intramolecular relaxation and solvation of the styryl dye LDS-751 dissolved in various solvents have been investigated by time-resolved stimulated emission fluorescence depletion technique. A suitable three-stage dynamic model is developed to interpret the observed ultrafast evolution of the fluorescence depletion with the time scale from several tens of femtoseconds to several hundreds of picoseconds. These three specific time regions, which strongly depend on solvents, are assigned to intramolecular relaxation, solvation, and fluorescence lifetime decay, respectively.