radiation. This result, which is in striking contrast to the ordinary phenomena of selective absorption, can be simply explained on Kossel’s view. The simple reverse of the process corresponding to the emission of, for instance,
would necessitate the direct transfer of an electron from ring 1 to ring 2, but this will obviously not be possible unless at the beginning of the process there was a vacant place in the latter ring. For the excitation of any line in the
radiation, it is therefore necessary that the electron should be completely removed from the atom. Another consequence of Kossel’s view is that it should be impossible to obtain the
series of an element without the simultaneous emission of the
series. This seems to be in agreement with some recent experiments of C. G. Barkla[35] on the energy involved in the production of characteristic Röntgen radiation. From these examples it will be seen that even if Kossel’s considerations will need modification in order to account in detail for the high frequency spectra, they seem to offer a basis for a further development.
As in the [former section], it is assumed that the spectra considered above are due to the displacement of a single electron. If, however, several electrons should happen to be removed from one of the rings by a violent impact, the considerations at the end of the [former section] would not apply, since the electrons removed in this case can be replaced by electrons in the other rings. We might therefore possibly expect that the rearrangement of the electrons, consequent to the removal of more than one electron from a ring, would give rise to spectra of still higher frequency than those considered in this section.