Resonant x-ray diffraction study of a new brominated chiral SmCA* liquid crystal

We present a new high energy resonant x-ray scattering study of a brominate d chiral liquid crystal material exhibiting antiferro, ferri and ferroelect ric smectic C phases. The absorption K-edge of bromine is at much higher en ergy (13.49 keV) than the sulfur K-edge (2.47 keV) which should enable a wi der variety of experimental geometries. A weak resonant signal is detected on free standing films in the SmCA* phase only. Interestingly, the signal i s stronger in binary mixtures with a bromine free thiobenzoate compound. Th is observation suggests that most chiral liquid crystal structures could be studied by resonant scattering after incorporation of a molecule bearing a resonant atom as a probe. Resonant x-ray diffraction profiles are also cal culated for some recently proposed distorted clock models of the 4-layer fe rrielectric phases. Finally the influence of defects is investigated.