X-Ray Spectra

Abstract

IT was shown by Barkla and Sadler (Phil. Mag., February, 1907, and October, 1908) that many elements, when subject to a suitable beam of X-rays, emit a homogeneous beam of secondary X-rays of penetrating power characteristic of the radiating element. One of the writers (Barkla, Proc. Camb. Phil. Soc., May, 1909) showed that various groups of these characteristic radiations exist, and that each element most probably emits a line spectrum of X-rays, each line moving to the more penetrating end of the spectrum, with an increase in the atomic weight of the radiating element. For no single element, however, was the homogeneity of more than one radiation proved, or the penetrating power accurately determined. As all the principal phenomena accompanying the transmission of X-rays through matter are determined by the spectra of the constituent elements, it became a matter of considerable theoretical interest to confirm the theory by demonstrating the homogeneity of various radiations from some particular element. The writers therefore chose several of those elements the characteristic radiations of which were expected to be well within the range of penetrating power comparatively easy to experiment upon.