Picosecond polarized fluorescence studies of anisotropic fluid media. II. Experimental studies of molecular order and motion in jet aligned rhodamine 6G and resorufin solutions

New polarized time resolved fluorescence techniques are implemented to determine the full angular motion of a probe molecule in an anisotropic environment. Studies of rhodamine 6G and resorufin molecules aligned in a free ethylene glycol jet show that the presence of net molecular order is accompanied by a distinct anisotropy in alignment relaxation following photoselection. Diffusion coefficients for phi and theta motion (D(parallel to) and D(perpendicular to)) in a jet fixed axis system are determined from the cylindrically symmetric and asymmetric alignment relaxation rates for the isotropic and anisotropic regions of the jet. The presence of net negative molecular alignment as the free jet is formed is seen to correspond to restricted phi motion (D(parallel to) < D(perpendicular to)), with a net positive steady state alignment the anisotropy in the diffusion dynamics is reversed. The differences in D(parallel to) and D(perpendicular to) are attributed to anisotropy in the solvent viscosity as a consequence of flow. The combination of linear and circular polarization techniques is seen to provide useful information on cylindrical asymmetry and relaxation dynamics hitherto unobserved by conventional fluorescence polarization techniques. (C) 2000 American Institute of Physics. [S0021-9606(00)00217-8].