β-ray spectra and their meaning

Abstract

In a previous paper, I described some measurements of the magnetic spectrum of the β-ravs ejected from various metals by the γ-rays of radium B. These experiments showed that the conversion of monochromatic γ-rays into β-rays was described by the same quantum relation that holds for X-rays and light, and using this knowledge it was found possible to give a complete explanation of the natural β-ray spectrum of radium B. Sir Ernest Rutherford had already shown that the lines in the β-ray spectrum were due in some way to the conversion of monochromatic γ-rays in the same radio active atom that emitted them, and these experiments on the excited spectra now proved that the strong lines were due to the conversion of the γ-rays in the K ring, and the weaker lines to conversion in the L 3 ring. This explanation of the line β-ray spectrum is, by itself, of considerable interest, but of far greater importance is the fact that these experiments give a method of finding the wave-lengths of γ-rays. The shortest wave-length that has been measured by the crystal method is 0·07 Å. U., and at present it seems almost impossible to extend this range much further by this method. Since many radio-active bodies emit γ-rays of shorter wave-length than this any method by which these wave-lengths may be found is important