High-speed scans of the luminescence spectra of rhodamine 6G and B solutions excited by ultrashort light pulses

The results are given of an investigation of the kinetics of the luminescence spectra of rhodamine dyes carried out using a fast shutter based on the optical Kerr effect. The measurements were carried out during a period of 2–100 psec from the beginning of an exciting pulse and they demonstrated that during this period the luminescence spectra did not change but were identical with the time-integrated spectra determined under the same excitation conditions. However, the shape and position of the spectra changed considerably when excitation with continuous low-power radiation was replaced with high-power ultrashort laser pulses. This was due to the possibility of formation of excited stereoisomers of the dyes.