An investigation of the total reflection of soft X-rays.

The design and construction of a vacuum reflectometer for the study of the total reflection of soft X-rays is described. The instrument, which uses a plane mica monochromator and a proportional counter detector, was used to obtain curves of reflecting power versus glancing angle for a number of characteristic wavelengths in a region previously neglected by experimenters. New data is given for reflection by optical flats of glass and stainless steel. These results are used to test (a) the Fresnel equations for reflection, modified to take account of absorption and (b) the theories of X-ray dispersion. From the discrepancies between theory and experiment, conclusions are drawn regarding the surface structure of the specimens. Some results are also given for evaporated films of copper and ytterbium fluoride. From the latter, it would seem that the Drude-Lorentz dispersion theory holds near an X-ray absorption line.