The Effect of the Magnetic Field on the Absorption of X-Rays

Abstract

Effect of a magnetic field on the absorption of x-rays, if it can be measured, would have an important bearing on the theory of atomic structure. Since the effect is very small, a differential method was adopted and by eliminating various spurious effects the apparatus was made sensitive enough to detect a change of 1 part in 10,000. Observations were made with a peak voltage of 80 kv. across the Coolidge tube (mean wave-length about 0.3 Å.) and with a magnetic field $H$ of about 18,000 gauss. For $H$ perpendicular to the rays, aluminum, carbon, copper, iron, nickel, platinum, zinc, and silver showed changes in absorption coefficients of + 8 ± 6, - 5.6 ± 2, + 0.8 ± 0.4, - 10 ± 2, + 1.6 ± 0.5, + 1.7 ± 0.4, - 1.2 ± 0.4 and + 1.6 ± 0.8 parts in 10,000 respectively, while with $H$ parallel to the rays the corresponding changes were + 2.7 ± 1, + 3 ± 1, + 1.4 ± 1, + 0.5 ± 2, + 0.7 ± 2, + 1.1 ± 1 and + 1.3 ± 1 × ${10}^{-4\mathrm{}}$, silver not being tried. These results are in accord with the hypothesis that the magnetic properties are largely determined by the outer shell or valency electrons, since at the wave-lengths used by far the greater part of the absorption is due to the inner electrons. Wood was also tested with softer rays having a mean wave-length of about 1.2 Å., and showed a change of + 80 ± 20 × ${10}^{-4\mathrm{}}$ as compared with 3 × ${10}^{-4\mathrm{}}$ for carbon for wave-length 0.3 Å. Following the suggestion of this result it is proposed to do further work with light elements and softer x-rays.