PHOTOISOMERIZATION DYNAMICS AND SPECTROSCOPY OF THE POLYMETHINE DYE DTCI

Laser absorption spectroscopy, laser-induced fluorescence, and pulsed- laser optoacoustic spectroscopy were used to characterize photophysica l and spectroscopic parameters of the photoisomer of the cyanine dye 3 ,3'-diethylthiacarbocyanine iodide (DTCI), Values for the photoisomeri zation and back-photoisomerization quantum yields (phi(NP) = 0.20 +/- 0.03 and phi(PN) = 0.16 +/- 0.03, respectively), as well. as values fo r absorption cross sections and the energy content of the ground state of the photoisomer, were obtained. The quantum efficiency of fluoresc ence of this species was found negligible. Similar to the findings for DODCI and Merocyanine 540, these results suggest that internal conver sion without passing through an intermediate twisted state is the main deactivation step for the excited photoisomer.