ROTATIONAL DIFFUSION AND LASER-INDUCED ORIENTATION OF DYE MOLECULES IN SOLUTION

The rotational motion of dye molecules in different solvents is invest igated by polarization method of picosecond spectroscopy. It is shown that ''superstick'' condition is realized for rotation of excited mole cules of 3-aminobenzanthrone, 3-aminocyclohexylbenzanthrone, and Nile blue oxazone A in alcohols. The time of rotational diffusion for these molecules in the excited state appears to be considerably longer than in the ground one. This difference may be used for angular orientatio n of a molecular ensemble in liquid. Computer simulation shows that a very high degree of light-induced diffusional orientation of molecules can be achieved under excitation and simultaneous quenching of dye so lution with two light beams of different frequencies and orthogonal po larization.