504 Radiations from Exploding Atoms [June 4, 



of the " K " characteristic radiation of that element. If this be the 

 case, it maj prove possible that a still more penetrating radiation 

 might be obtained from tungsten, but in order to excite it a voltage 

 of the order of a million volts would probably be required. In any 

 case, it seems clear that Planck's relation does not hold for excitation 

 of high frequencies by swift electrons, but may hold very approxi- 

 mately for lower frequencies corresponding to the radiation excited 

 by a few hundreds or thousands of volts. On the other hand, the 

 evidence obtained from a study of the /? rays excited by X-rays or 

 7 rays certainly indicates that the relation E=jt?^v holds at any rate 

 very approximately for the highest frequency examined. It is thus 

 obvious that the emission of /? and y rays from the radio-active 

 atoms is clearly connected with the general theory of radiation, and 

 it seems likely that a close study of these radiations will throw much 

 light on the mechanism of radiation in general. 



There can be little douljt that the penetrating y rays from active 

 matter have their origin in the vibration of electronic systems in the 

 structure of the atom outside the nucleus. The nucleus itself, how- 

 ever, must be violently disturbed by the expulsion of an a or yg 

 particle. If this leads to the emission of a y radiation, it must be 

 of exceedingly high frequency, as the forces holding together the 

 component parts of the nucleus must be exceedingly intense. We 

 should anticipate that this radiation would be extraordinarily pene- 

 trating, and difficult to detect by electrical methods. So far no 

 experimental evidence has been obtained of the existence of such 

 veiy high-frequency radiations, but it may be necessary to devise 

 special methods before we can hope to do so. 



[E. R.] 



