Abstract
The study of the Raman intensity of the ‘breathing’ mode of the benzene rings as a function of the temperature in smectic phases revealed strong anomalies of the intensities IZZ and IYY in SmCFI2* and SmCFI1* phases, as well as an important shift of the principal optical direction with respect to other smectic phases. The analysis of these results provided evidence for significant structural changes at the SmC*–SmCFI* and SmCFI*–SmCA* phase transitions, because the molecules can no longer be treated as cylindrical rods. No anomalies in the tilt angle were found. Experimental results suggest a relationship between the deviation of the optical axis and the particular structure of the SmCFI* phases. The deviation of IZZ maxima as a function of the rotation angle Ψ and the behaviour evident under an electric field in SmCFI* and SmCA* phases clearly excludes the coexistence of SmCA* and SmC* local domains in SmCFI* phases.