270 Dr. L. Vegard on the X-Ray Spectra 



Although the deviation d has the right sign and the right 

 type of variation with N, its absolute magnitude is by far 

 too small to account for the observed deviations from 

 Kossel's relation. 



The Frequency of the Absorption Edges. 



§ 15. We assume that the necessary condition for absorp- 

 tion to take place is that the energy quantum hv of the 

 incident ray is equal to or greater than the energy which is 

 required to remove an electron from its place in the atom 

 and bring it to an infinite distance with a velocity equal to 

 zero. Let this energy be AE, then : 



/>v~AE, 



. 01 if va is the frequency of the absorption edge : 



hv A =AE. 



Assuming that during the removal the angular momentum 

 of the remaining electrons is kept unaltered, we found that 

 the expulsion of an electron from a ring-system would be 

 accompanied with a change of energy of all electronic 

 systems outside the broken one. 



We mentioned the possibility that this change of energy 

 escaped in the form of radiation ; but it is perhaps more 

 likely that it is spent on the escaping electron. 



This latter assumption would mean that each electron left 

 behind in the rings at any moment during the time of escape 

 keeps its angular momentum unaltered, and this tendency to 

 keep a constant momentum is equivalent to a force which is 

 exerted on the escaping electron, and which on an average 

 is directed away from the nucleus. 



If, however, no energy is wasted by radiation during the 

 escape of the electron, the energy necessary to remove the elec- 

 tron to infinity must be equal to the energy which must radiate 

 out when the electron recombines from infinity to its original 

 position. 



Let us suppose the recombination to take place in one 

 step, or, that only one energy quantum of frequency v m is 

 emitted ; then : 



kv x =A'E = hv A or 



Consequently v^ should be equal to the frequency of the 

 absorption edge. 



