Photoisomerization dynamics of DODCI studied by spectrally resolved fluorescence decay measurements Original Research Article

The organic dye DODCI (3,3′-diethyloxadicarbocyanine iodide) in methanol and ethylene glycol is excited with picosecond light pulses at 527 nm (dominant N-isomer excitation) and the time dependence of the N-isomer and P-isomer fluorescence is monitored with a spectrometer-streak camera system. The slowed-down non-exponential N-isomer fluorescence and the time-delayed P-isomer fluorescence indicate S1-state photoisomerization via an intermediate state (M). The energetic position of this intermediate state is determined. The formation of a further photoisomer (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.