Total Reflection of X-Rays from Nickel Films Part II

Abstract

Variation of critical angle with thickness of film for films deposited on platinum. —The total reflection of x-rays ($\lambda =0.707\mathrm{}\mathrm{A}$) is obtained from a series of thin nickel films of thickness varying from zero to 2.05×${10}^{-5\mathrm{}}$ cm. The films were sputtered upon thick platinum which was, in turn, sputtered upon a glass support. The critical angle for each film was measured. The values of the critical angle varied from 0.0040 radians (that of the bare platinum) to 0.0034 radians. With the exception of an increase in the critical angle (maximum value of 0.0043 radians) for the thinnest films, the critical angle decreased logarithmically with increasing thickness of the nickel film. The value obtained from the thickest film agrees with that calculated by the Lorentz dispersion formula. These results, together with those reported earlier seem to prove conclusively that the phenomenon of total reflection is not a purely surface phenomenon but is one which requires a layer of metal of probably definite thickness for the particular reflecting matter and wave-length of radiation used. An explanation for the variation of the critical angle with the thickness of the nickel films is given. This is based upon the assumption that the contribution to the intensity of the reflected ray made by the deepest electrons will be effective only when the total length of the path of the radiation in the metal is not too great. The maximum effective depth is that which reduces the intensity of the emerging radiation by absorption to a value less than that which may be detected in the reflected beam.