EXCITATION TRANSFER FROM AZO-DYE TO NEMATIC HOST DURING PHOTOISOMERIZATION

Dynamic holography and polarimetric techniques are used to study the p hotoisomerization kinetics of D2 bisazo dye and the excitation transfe r from dye to nematic liquid crystal host. As a result of this transfe r, transient modulation of the orientational order parameter, three-di mensional long-scale molecular transient rotation and equilibrated two -dimensional molecular rotations are identified in the host. Amplified rotation of nematic molecules is observed which is much more efficien t for the dye photoexcitation with a wavelength in the red rather than in the blue side of its absorption band. The possible role of dye pho toisomerization mechanism in these processes is discussed. The dynamic character of the dye induced torque and the presence of long-living i ntermediate states during photoisomerization and their diffusion are s uggested. (C) 1997 American Institute of Physics.