Surface XPCS on nanometer length scales — What can we expect from an X-ray free electron laser?

We present a theoretical study of the feasibility of surface scattering experiments with X-ray photon correlation spectroscopy at the planned X-ray free electron laser (XFEL). We are calculating scattering cross sections, count rates, signal to noise ratios and time scales of capillary waves on liquid water, liquid mercury and liquid glycerol at nanometer length scales. The use of an X-ray delay line to produce arbitrary lagtimes in the correlation spectroscopy is discussed and demonstrated with the example of surface scattering. Estimates of sample heating during the intense XFEL pulse are given.