Coherent soft-X-ray dynamic light scattering from smectic-A films

We have used coherent soft-x-ray dynamic light scattering at the Bragg peak to measure the thermally driven layer fluctuations in freely suspended fil ms of five different smectic-A liquid crystals: 40.8, 70.7, 8CB, 80CB, and 100CB. The measured relaxation times at a scattering wave vector correspond ing to the interlayer spacing (2 pi q(-1) approximate to 30 Angstrom) range d from 2 to 60 mu s for films from 4 to 50 mu m thick. Thus, we have achiev ed the same time resolution as conventional laser dynamic light scattering, but with 100 times higher spatial resolution.