Connexion between ft and 7 Ray Spectra. 319 



rocksalt at angles of 15 0, 5 and 17°' 15. From analogy with 

 the case of ft rays from a radio-element, it is to be anticipated 

 that with a high voltage discharge, the nickel radiation 

 would consist of a train of one or more waves each of energy 

 Jlv corresponding to the frequency v of each of the strong 

 lines of nickel. When this radiation falls on another 

 element, it is absorbed and partially converted into ft rays. 

 For a given frequency v lt we may suppose as before that the 

 excited ft rays would fall into groups of energy phv 1 — qhv 2 — A, 

 where q is an integer and v 2 is the frequency of the character- 

 istic radiations excited by the X rays in the element in 

 question. The general evidence indicates that the constant A 

 is negligible. If no characteristic radiation is excited, it is 

 to be expected that the energy of the groups of ft rays 

 should be given by phv l9 where p is an integer. If the 

 conversion of the X rays into ft rays is accompanied by the 

 characteristic radiation of the element, another series of lines 

 should make their appearance of energy given hj phv 1 — qliv 2 . 

 At the same time, the characteristic radiation of the frequency 

 v 2 would be partially converted into ft rays in escaping from 

 the substance and would thus be expected to give rise to 

 groups of ft rays of energy qliv 2 , where q is an integer, and 

 so on. 



It is obvious, that on these views, the spectrum of the 

 ft rays excited by the passage of only one frequency of X 

 radiation through matter may show a very complex /3-ray 

 spectrum, consisting of a number of distinct groups of ft rays. 

 If the primary radiation consists of a number of frequencies, 

 the resulting /3-ray spectrum will probably prove as complex 

 as the /3-ray spectrum of radium B or radium C. 



A preliminary examination of the /3-rav spectra excited in 

 different elements by the characteristic radiation of nickel 

 has been made by Robinson and Rawlinson*. They have 

 found that the magnetic spectrum of the ft rays does show 

 the presence of a number of well-marked groups of ft rays, 

 but the experimental evidence is not yet complete enough to 

 test the correctness of the above point of view. 



University of Manchester, 

 June 30, 1914. 



* Phil. Mag. August 1914. 



