Detection and investigation of photoinduced transient states of organic dyes by non-linear probing method

摘要

The absorption of high intensity laser light by dye molecular probes may produce non-linear effects. They result in both bleaching and darkening, which depends on the rates of depopulation/repopulation of the ground S{sub}0 and excited S{sub}1 states. It is shown, that the darkening is the characteristic feature of fast photophysical and photochemical reactions occurring in the S{sub}1 state. This suggests a very simple method for detection and study of these reactions. The method is tested for photoinduced proton transfer and solute-solvent structural reorganizations in polymethine dyes. The results suggest, that the dye probes exhibiting these reactions may be applied for visualization of protonic gradients, microviscosity and distribution of different substances within the living cells. The method is based on the comparison of light transmission images at low and high intensities. It is extremely simple and fast, a single light pulse may be sufficient to create the image.