140 Beta-Ray Emission from 1 Kin Films. 



accuracy, the results of this part of the work must be taken 

 qualitatively rather than quantitatively. 



I desire to express my thanks to Professor O.W. Richardson 

 for his kind interest in this work. 



The general conclusions maybe summarized as follows: — 



(1) It is improbable that the maximum speed of ejection 

 of electrons from different substances under the influence of 

 X-rays of definite wave-length is exactly constant indepen- 

 dently of the nature of the substance, and dependent only 

 upon the frequency of the incident X-rays. These experi- 

 ments have shown that throughout the whole range of motion 

 the distribution of electrons depends fundamentally upon the 

 substance from which they are emitted, but. the difference, 

 if any, in the maximum velocities is too small to be demon- 

 strable by this method. 



(2) The experimental results point to the conclusion that 

 there may be speeds of emission of electrons from an atom 

 (S) when X-rays of frequency v fall upon it given by 

 either 



l-mv 2 = hv — B (7w K + liv Ji + hv M +...), 



each successive speed being given by the removal of a term 

 from the bracket, commencing with the term, or 



±mv 2 = hv — s (/<l>) 



K or L or ilj 



the expression in brackets representing the potential energy 

 of the electron from whichever atomic ring it was ejected, 

 v K , v L etc. being the K, L, etc. frequencies of the X-ray 

 spectral lines of tiie parent atom (S). The experimental 

 data agree rather better with the latter expression. 



(3) There is a type of electronic emission fundamentally 

 associated with each type of X-ray emission. Assuming 

 that it is not a necessary condition that each of the radiating 

 atoms of one substance should be emitting all possible types 

 of spectral lines, from those of highest energy downwards, 

 then the energy of electronic emission of any one of these 

 atoms is complementary to that of its wave-emission ; in 

 other words, the "K" electron is the slowest on emergence, 

 the concomitant " L " electron faster, and so on. 



