Soft X-rays from Heavy Elements, Tantalum to Gold

Abstract

Soft x-radiations from tantalum, tungsten, osmium, iridium, platinum and gold, excited by electron bombardment at voltages between 30 and 1500 volts, were studied by the use of Kurth's apparatus in which the photo-electric effect of the radiation per unit electron current is measured. In this range for each metal from 6 to 9 critical voltages were located to within about 5 per cent. The results are in fair agreement with the values Bohr and Coster predicted for the ionization potentials of the N-level electron orbits, by means of the combination principle, from the x-ray wave-lengths measured by Siegbahn and others. The limitations of the method are considered and also the extent to which agreement is to be expected between the two different methods of measuring the energies of these levels.