Quasielastic light-scattering measurements are reported for a chiral smectic-C material as a function of enantiomer concentration and applied electric field. The elastic constant ${\mathit{B}}_1$ and associated viscosity have been determined. More importantly, it was found that ${\mathit{B}}_1$ is composed of a bare part ${\mathit{B}}_1^0$ and a polarization-dependent part ∝${\mathit{P}}_0^2$/${\mathit{q}}^2$. For q<${10}^5$ ${\mathrm{cm}}^{\mathrm{-}1}$, the polarization-dependent term is much larger than ${\mathit{B}}_1^0$.

• Received 17 April 1992

DOI:https://doi.org/10.1103/PhysRevLett.68.3575