SPIN RELAXATION BY DIFFUSION ON BIAXIAL RODS

A theoretical framework is presented for the analysis of orientation a nd frequency dependent spin-relaxation rates from nuclei-diffusing on biaxial rodlike aggregates in rectangular and other amphiphilic liquid crystals. With the aid of eigenfunction expansion and integral transf orm techniques, the problem of calculating the spectral density functi ons for surface diffusion on a biaxial rod can be reduced to quadratur e, without the need to specify the rod geometry. The general results a re applied to ribbonlike and elliptic rods, yielding analytical result s. The calculations demonstrate that spin relaxation is a considerably more sensitive probe of interface curvature than the static line shap e. The relaxation anisotropy, in particular, can discriminate between closely similar rod geometries with different curvature distributions. (C) 1997 American Institute of Physics.