An Experimental Investigation of the Energy of the Characteristic K-Radiation from certain Metals

Energy of K-radiation from Cr, Cu, Rh, and Ag, for applied voltages to 45 kv.—Using a special Coolidge tube with a thin mica window, and a rotatable anti-cathode on which were mounted four metals, the intensities of the characteristic K x-rays from Cr(atomic number 24), Cu(29), Rh(45), and Ag(47), corrected for general radiation, for incomplete absorption in ionization chamber, for incomplete reflection by crystal, and for absorption by mica window, were found to be approximately linear functions of the square of the applied voltage on the tube. The ratio of the intensities of the $\alpha$ and $\beta$ radiations was constant for each metal and decreased regularly with increasing atomic number from 7.36 for Cr to 4.65 for Ag. The ratio of the $\alpha$ radiation to the general radiation also decreased, but more markedly, from 25 for Cr to 11.2 for Cu and 2.7 for Ag. Comparison with the theory of Bergen Davis shows good agreement for Ag and Rh, but not for Cr and Cu. This is probably due to the fact that the theory neglects the fluorescent re-emission of absorbed general radiations.