X-ray reflectivity studies at sub-second resolution

Full text: We are currently developing an instrument -ultimately one that exploits the high radiation flux of a synchrotron source- that will record reflectivity measurements of fast, transient structural changes in chemical and biological processes at the air-water interface with sub-second resolution. Present methods for the study of materials that show no appreciable structural change are very powerful. However, there is a need to improve the time resolution of such studies from hours to fractions of one second (potentially to milliseconds with synchrotron radiation) so that faster chemical reactions and the relaxation processes of interfacial structures can be investigated in real time. Two energy dispersive analysers for the new reflectometer have been commissioned on our laboratory x-ray source: a commercial liquid nitrogen-cooled germanium detector (EG and G); and a Bragg rotor crystal analyser, designed and constructed at the Research School of Chemistry. Since reflectometry is a technique well suited to study the profile of solid state metal oxide and metal organic thin films, we will at no loss of generality, discuss the fundamental issues of the new spectrometer in the context of this application