Molecular organization in the twist-bend nematic phase by resonant X-ray   scattering at the Se K-edge and by SAXS, WAXS and GIXRD
  Using a novel Se-labelled dimer mixed with DTC5C7 aligned by magnetic field, the twist-bend nematic phase (Ntb) in dimers was studied by hard X-ray resonant scattering and by small and wide angle X-ray scattering (SAXS, WAXS). Resonant diffraction spots indicated a helix with a 9-12 nm pitch in the Ntb phase. Unprecedentedly high helix orien-tation enabled deconvolution of global and local order parameters. This, combined with simultaneous resonant and non-resonant SAXS and WAXS data, allowed us to construct a modified model of the Ntb phase matching twisted molecular conformations and the local heliconical director field. 
W. D. Stevenson, Z. Ahmed, X. B. Zeng, C. Welch, G. Ungar and G. H.   Mehl
cond-mat.soft