Single and three pulse photoselection of dye probes in nematic liquid crystals

We present results of single and three pulse photoselection studies of the dynamics of a fluorescent probe (Oxazine 4) in the nematic phase of the liquid crystal 4-n-pentyl-4'-cyanobiphenyl (5CB). The combination of these techniques with time resolved fluorescence anisotropy measurements allows the unambiguous determination of the full angular motion of the probe together with the ground and excited state degrees of equilibrium (steady state) alignment. The restricted geometry imposed by the nematic host is seen to impart a marked anisotropy in theta and phi diffusion (gamma(phi)/gamma(theta)similar to4)