ABSTRACT
Brownian rotational diffusion is characterized by exponential correlation functions. In the fast-motion regime, the rotational correlation time (or diffusion coefficient) is determined by differential broadening of the -hyperfine lines. Consistent values from the different lines indicates isotropic rotation; otherwise the diffusion is axially anisotropic. High-field/frequency EPR yields the full diffusion tensor for completely anisotropic rotation in the fast regime. In the slow-motion regime, diffusion coefficients are determined by spectral simulation with the stochasticLiouville equation. Line splittings and linewidths yield empirical calibrations in the region approaching the rigid limit. A valuable summary is given in the concluding section of the chapter.
