X-Ray Spectra of Long Wave-Length

Abstract

Method of obtaining x-ray spectra by reflection from a concave grating.—The paper describes a photographic method of obtaining x-ray spectra of long wave-length, based on the experimental fact that x-rays are totally reflected from a mirror (or grating) provided the angle of incidence is sufficiently large. Details are given of a vacuum spectrograph employing an x-ray tube as a source of radiation, in conjunction with a two-metre concave grating. About fifteen lines have been measured between 40 and 200A. As it has not yet been possible to obtain a pure spectrum of any one element, the interpretation of these lines is a matter of considerable uncertainty. Nearly half of them appear to be due to strontium and barium deposited on the anticathode from the oxide coated filament of the x-ray tube. The method is applicable to all wave-lengths greater than about 20A.