﻿570 Mr. D. Coster on the Spectra of X-rays 



the relative intensity of these lines in regard to the line fi 2 

 was observed. Photographed with the higher tension, how- 

 ever, they seem to be much more intense on their long 

 wave-length side than on the other side. This difference 

 was not observed on the plates taken with the lower tension. 



I intend to continue these researches, using a direct- 

 current source o£ high tension. 



§ 8. From these results and the considerations of the 

 former paragraphs it is evident that we cannot agree with 

 the theoretical interpretation given by Mr. Wentzel of the 

 fine structure of the absorption discontinuities. It is well 

 known that the researches by Fricke*, Stenstrom f , and 

 Hertz % showed that at a short distance from the principal 

 discontinuity another discontinuity may be found. The 

 photographs give the impression that there are two white 

 lines ; the most intense of which usually lies on the long 

 wave-length side. From this we may conclude that two 

 different, rather definite, frequencies are selectively absorbed. 

 According to Wentzel, the principal discontinuity should be 

 connected with the removal of the first electron from the 

 corresponding shell to the outside of the atom, the second 

 with the removal of the second electron. As it seems very 

 improbable that this successive ionization really takes place, 

 it seems to be more likely that this structure of the absorp- 

 tion-edge is connected with the conditions at the outer side 

 of the atom, as has been suggested by Kossel §. In this 

 connexion it may be pointed out that in this laboratory 

 Mr. Lindh has found rather great differences for the wave- 

 lengths of the principal discontinuities of the same element 

 in different chemical compounds. 



§ 9. For the elements Ti (22), V (23), and Or (24) Fricke 

 also found a second discontinuity lying on the long wave- 

 length side of the principal discontinuity. It is very probable 

 that this anomalous discontinuity, as already has been sug- 

 gested by Wentzel, is connected with the completion of the 

 inner M-shell, which, according to Bohr, takes place in the 

 neighbourhood of the iron group. I shall give an explana- 

 tion of the appearance of this anomalous discontinuity, which 

 differs from that given by Wentzel in some essential details. 

 Wentzel suggests that in the region of the iron group the 

 M-shell may occur in different modifications in different 

 atoms of the same element, and especially that there are 



* Fricke, Phys. Eev. xvi. p. 202 (1920). 



t Stenstrom, Dissertation Lund, 1919. 



% Hertz, Zeitschriftf. Physik, iii. p. 19 (1920). 



§ Kossel, Verhandlwigen d. D. Phys. Ges. xviii. p. 339 (1916). 



