Abstract

The initial relaxation of photoexcited organic dye molecules occurs on a sub-picosecond time scale and has been the subject of several studies. Recent developments in experimental apparatus have significantly improved both the amplitude and time resolution of these experiments. We have employed the equal-pulse correlation technique to observe a saturation effect in the transmission of short pulses through a thin jet of organic dye in solution. Measurements of the relaxation of Nile Blue 690 clearly reveal a fast component with a decay time of 70 fs as well as a slower process which has been observed by other workers. We have also studied the ultrafast relaxation of the triphenyl methane dye Malachite Green, which is dominated by a strong internal conversion mechanism. Data from transmission correlation experiments performed on this dye exhibit a rapid oscillatory decay following photoexcitation as well as the previously-identified process with a decay time of 5 ps.

© 1986 Optical Society of America