Quasielectric Rayleigh Scattering in a Smectic-CLiquid Crystal

Using light-beating spectroscopy, we observe the Rayleigh scattering from a smectic-$C$ monodomain of $\mathrm{d}\mathrm{i}-(4-n-\mathrm{d}\mathrm{e}\mathrm{c}\mathrm{y}\mathrm{l}\mathrm{o}\mathrm{x}\mathrm{y}\mathrm{b}\mathrm{e}\mathrm{n}\mathrm{z}\mathrm{a}\mathrm{l})-2-\mathrm{c}\mathrm{h}\mathrm{l}\mathrm{o}\mathrm{r}\mathrm{o}-1-4-\mathrm{p}\mathrm{h}\mathrm{e}\mathrm{n}\mathrm{y}\mathrm{l}\mathrm{e}\mathrm{n}\mathrm{e}\mathrm{d}\mathrm{i}\mathrm{a}\mathrm{m}\mathrm{i}\mathrm{n}\mathrm{e}$. The signal is attributed to thermally excited relative rotations of smectic layers as proposed by de Gennes. We discuss the anisotropy of the elastic and viscosity coefficients involved in this mode, by comparison with the nematic situation.