James M. Forsyth

The Reflecting Properties of Soft X‐Ray Multilayers

We treat a variety of problems in the theory of soft x‐ray multilayer mirros. A characteristic matrix solution to Maxwell’s equations is presented that applies to both periodic and non‐periodic reflectors whose layers an possess arbitrary index gradients. Procedures are derived to maximize multilayer refletivity in the kilovolt and sub‐kilovolt regime. A refractive correction to Bragg’s law is derived that includes the effect of absorption as well as the effect of dispersion. Multilayer reflectivity in the presene of random thickness errors is treated analytically. An analytic treatment of different kinds of interfacial roughness is described. The reflecting properties of the multilayers may contain qualitative signatures that are characteristic of the different kinds of roughness. The effect of interlayer diffusion is discussed.

[36] Application of nanosecond X-ray diffraction techniques to bacteriorhodopsin

Publisher Summary This chapter presents the application of nanosecond X-ray diffraction techniques to bacteriorhodopsin (BR). The magnitude of any conformational change that may take place during the BR photocycle is under debate. The resolution of this question can be answered by use the newly developed laser plasma X-ray source to obtain subnanosecond X-ray diffraction patterns throughout the course of the 20-msec photocycle. To generate the purple membrane diffraction pattern, the single-beam Nd+3glass development laser is used. Experiments are performed with highly chlorinated targets; room temperature Saran (C2H2C12) and pressed polycrystals of hexachloroethane (C2Cl6) held at 77 K and X-ray powder diffraction pattern from a purple membrane stack recorded on 2475 high-speed recording film. The information contained in these powder patterns can be used along with the phase information obtained from electron diffraction studies to yield a two-dimensional projection of the electron density of the purple membrane perpendicular to the plane of the membrane. This view offers a great deal of information about BR because its seven helices are arrayed roughly perpendicular to the membrane plane—for example, the projection looks down the helical chains.