The reflection and diffraction of X-rays

Abstract

The agreement between the theories of the reflection of X-rays by solids and observations is discussed. Generally the observations so far obtained are not in close agreement with each other or with theory. The writers find that X-rays of wave-lengths 13·3 Å. (Cu Lα) and 44·7 Å. (C Kα) are reflected by glass, quartz and stainless steel at angles considerably greater than the calculated critical angles. The radiation from carbon has been focussed by a spherical mirror for an angle of incidence of 45°. The ratio of the intensity of the reflected to the incident beam, when X-rays from a carbon target are incident on a glass mirror, has been determined approximately by a photographic method and is found to agree with the Fresnel electromagnetic theory provided a higher absorption of the X-rays occurs than has been previously supposed. This evidence of reflection for angles of incidence greater than the critical angle, which is 6° for glass at a wave-length of λ = 44·7 Å., is confirmed by observations with a glass diffraction grating with which the λ = 44·7 Å. line has been observed for angles of incidence on a plane grating up to 19°. A new plane ruled grating spectrometer is described by means of which the C Kα line has been obtained with short exposures in all orders from the 18th negative to the 13th positive. Microphotometer curves of the wave-length distribution of the energy in the grating spectrum of carbon radiation are given, and these indicate that it consists almost entirely of the Kα line, λ = 44·7 Å. Using Rowland’s method of coincidences the wave-length λ C kα is found to be 44·7 5 Å. relative to λ Cu Lα = 13·32 Å.