  We investigate the dynamic behavior of long guest rod-like particles immersed
in liquid crystalline phases formed by shorter host rods, tracking both guest
and host particles by fluorescence microscopy. Counter-intuitively, we evidence
that long rods diffuse faster than short rods forming the one-dimensional
ordered smectic-A phase. This results from the larger and non-commensurate size
of the guest particles as compared to the wavelength of the energy landscape
set by the lamellar stack of liquid slabs. The long guest particles are also
shown to be still mobile in the crystalline smectic-B phase, as they generate
their own voids in the adjacent layers.
