A. Brognara, P. Pasini, C. Zannoni, Rototranslational diffusion of biaxial probes in uniaxial liquid crystal phases, J. Chem. Phys.,112, 4836-4848 (2000)

We discuss the problem of rototranslational diffusion of a rigid biaxial molecule dissolved in a uniaxial smectic liquid crystal phase. We examine distorted rod and disk like molecules and show how biaxiality and
roto-translational coupling can produce significant effects on some of the correlation functions and spectral densities most useful in analyzing experimental observables.
Here we see an example of the effect of translational diffusion for rodlike molecules

and for disclike molecules