Ultrafast physical effects in cyanine dyes subjected to tunable picosecond excitation

An analysis is made of the possibility of employing picosecond absorption spectroscopy based on continuously tunable excitation and probe sources in the investigation of complex kinetic processes. The results are presented of an investigation of various cyanine dyes. Calculations are made of the extinction coefficient of the excited state of one of the dyes. It is shown that the photoisomer 1,1'-diethyl-2,2'-monocarbocyanine, not observed previously, is formed within less than 50 psec.