Connexion between ft and y Ray Spectra. 309 



to be anticipated that characteristic y rays will always 

 accompany a line-spectrum of ft tsljs. This seems to be in 

 harmony with radioactive data. Radium E_, which gives 

 rise to a continuous /3-ray spectrum, emits exceedingly little 

 7 radiation in comparison with typical ft and 7 ray products 

 like radium B and radium C, which give well marked 

 spectra for both ft and y rays. 



While it would appear probable that the greater part of 

 the y radiation from radium B and radium C is composed 

 of several groups of rays of definite frequencies, no doubt a 

 small part of the y radiation gives a continuous spectrum. 

 Such a result is to be anticipated from analogy with X rays. 

 This general radiation probably has its origin in the electronic 

 collisions of an ordinary type when the ft particle is escaping 

 from the atom or to the passage of the ft particle close to the 

 nucleus. 



Importance of direction of escape of a ft particle : 

 There is another very interesting point that arises in 

 consideration of this question. "Why does radium E, which 

 emits ft rays of great intensity and over a wide range of 

 velocity, not emit y rays at all, or at any rate in very small 

 amount compared with radium B or radium C ? There 

 appears to be no reason to suppose that radium E would not 

 give rise to characteristic radiations of a frequency corre- 

 sponding to its atomic weight or atomic number when 

 bombarded by cathode rays of suitable speed. In order to 

 explain this anomaly, it appears necessary to assume that 

 the primary ft particle from a given radioeleinent is always 

 expelled in a fixed position with regard to the structure 

 of the atom itself. Considering the remarkably definite way 

 in which the atom of the same substance disintegrates, this 

 assumption does not seem improbable. On this view, the 

 absence of y rays from radium E is due to the fact that the 

 direction of escape of the ft particle does not pass near or 

 through the definite regions where characteristic radiations 

 are set up, and in consequence only a continuous spectrum of 

 ft rays is observed. An explanation may be given on similar 

 lines of many remarkable anomalies in the types and relative 

 intensities of 7 rays emitted from radioactive substances. 

 This is well illustrated by a comparison of the 7 rays from 

 radium B and radium C which are nearly of the same atomic 

 weight. Radium B emits a very soft radiation which is 

 almost entirely absent in radium C, while radium B does not 

 emit the very penetrating radiation observed from radium 0. 

 We must suppose that the ft particle from radium B passes 



