1124 Prof. It. Whiddington on 



that the rhodium target emits — in addition to "white 

 radiation — a very strong monochromatic radiation RhKa 

 [v = 490xl0 16 ], together with a much feebler frequency 

 RhK^ [> = 551 xlO 16 ]. 



If the radiations characteristic of the element under 

 consideration are excited, it will be necessary to take 

 into account also the radiation frequencies K a , Kjg ... in 

 the K series and La, L/s ... in the L series, M a , Mp ... in 

 the M series, etc., and also the corresponding absorption- 

 limit frequencies K, L, M . . . in the following manner : — 



The X-ray electrons — i. e. the electrons liberated by the 

 X radiation — will have energies corresponding to their 

 origin. Electrons liberated from the more deep-seated 

 rings nearer the nucleus will have less energy than those 

 liberated from the outer rings. 



Thus the Rha radiation may liberate electrons with 

 energies proportional to the frequency differences : 



RhKa — K (electron from K ring), 

 RhKa — L (electron from L ring), 



RhKa — M (electron from M ring), 



etc., etc. ; 



and if it be possible for the free electrons to absorb the X-ray 

 energy : 



RhKa (free electron). 



There may also be a much smaller liberation of electrons 

 corresponding to : 



RhK p -K, 

 RhK p -L, 

 RhK p -M, 



RhK p , 



producing much fainter impressions in the photographs. 



In addition to these sets of electrons, there may be other 

 sets liberated by the K, L, etc. X radiations excited in the 

 element under examination. 



The Ka line cannot liberate an electron from the K ring, 

 since its energy is not sufficient ; but there may be 

 K a — L (from L ring) K^ — L, 

 E.-M (from M ring) E^-M, 



K a (free electron ?) K s ; 

 and similarly for the L radiation, although in this case 

 the spectrum is somewhat more complicated by the presence 

 of a comparatively strong Ly radiation. 



