PHOTOISOMERIZATION DYNAMICS OF DODCI STUDIED BY SPECTRALLY RESOLVED FLUORESCENCE DECAY MEASUREMENTS

The organic dye DODCI (3,3'-diethyloxadicarbocyanine iodide) in methan ol and ethylene glycol is excited with picosecond light pulses at 527 nm (dominant N-isomer excitation) and the time dependence of the N-iso mer and P-isomer fluorescence is monitored with a spectrometer-streak camera system. The slowed-down non-exponential N-isomer fluorescence a nd the time-delayed P-isomer fluorescence indicate S-1-state photoisom erization via an intermediate state (M). The energetic position of thi s intermediate state is determined. The formation of a further photois omer (P2-isomer) emitting at the short wavelength side of the N-isomer is observed. Additionally the molecular reorientation is analysed by time-dependent fluorescence anisotropy measurements.