124: Mr. L. Simons on the Beta-Kay Emission from 



In the experiments described below some attempt has 

 been made to find a solution to the following problems : — 



1. Is the maximum speed of ejection of an electron from 



an atom entirely independent of the nature of that 

 atom and dependent only upon the wave-length of 

 the incident radiation ? 



2. Apart altogether from the question of the diminution 



in speed of emergence of those /3-rays which have 

 their origin in the deeper layers of the material, what 

 is the precise nature of the distribution of speeds 

 amongst the electrons emitted from the parent atoms 

 when these are exposed to X-rays? How is the 

 distribution affected by (a) the nature of the parent 

 atom, (b) the* wave-length of the incident radiation? 



3. If the existence of a #-ray " spectrum " can be proved,. 



what is the interrelation between each /S-ray spectral 

 line and the corresponding X-ray spectral line ? 



Apparatus. 



The method employed throughout was that due originally 

 to Beatty in his study of the absorption coefficients of the 

 /3-rays. A few modifications were introduced. It was 

 thought that the emission would be simplified by using only 

 very thin films of the various elements. These were As, Se, 

 Zr, Ag, Sn, Sb, Ba, Au, Pb, and Bi. The X-rays which 

 were incident upon these screens in turn were the so-called 

 homogeneous X-radiations, first from silver and secondly 

 from barium *. The primary beam of X-rays was produced 

 by a standard Coolidge tube, and every endeavour was made 

 throughout the whole of the work, a period of about eleven 

 weeks, to keep matters constant. The parallel spark, 

 between point and plate, backed up by the tube measured 

 four inches, and the current in the heating spiral was adjusted 

 so that the point and plate were always just on the point of 

 sparking. This current was four amperes throughout. The 

 barium secondary radiator was a flat cell of Ba0 2 , the front 

 of the cell being tissue-paper, the back card". When, this 

 was used an extra aluminium sheet 1 mm. thick was inter- 

 posed between it and the ionization chamber and other 

 apparatus in order to eliminate the characteristic L radiation 



* The fact that the so-called homogeneous K radiation consists of a 

 series of lines of different wave-lengths, whilst rendering •impossible 

 accurate measurements by this method, does not seriously interfere with 

 the main conclusions drawn herein. An attempt is being made to 

 employ really homogeneous radiations and to overcome the necessary 

 mechanical difficulties. 



