Measurement of molecular reorientational relaxation time by incoherent light with optical Kerr shutter

Abstract

We report, the first time to our knowledge, the measurement of reorientational relaxation time T of dye molecules dissolved in solution using incoherent light. In the experiment, an AO Q-switched and frequency doubled YAG laser with pulse width 150 ns long compared with the Tor was used, the measured dye molecules were Rh6G and RhB dissolved in different solvents. The transmitted intensity of the probe light was measured by changing the delay time t between the probe light pulse and pumping pulse. The resolution time was governed only by the coherence time tc of the laser light. A combined time constant T (1/T = 1/T1 + 1/Tor, T is the first excited state lifetime) was employed.