﻿1142 Prof. Horton and Dr. Davies : Ionization of Abnormal 



when helium atoms which were in an abnormal condition 

 were bombarded by electrons having energy in excess of 

 4*8 volts but less than 204 volts, and evidence is given 

 which shows that ionization can be produced -below 20*4 

 volts in this way. The attempts to demonstrate that such 

 ionization could be produced by electrons having only 

 4*8 volts energy, were, however, unsuccessful. More 

 recently further attempts to demonstrate this point satis- 

 factorily have been made by the authors, and although the 

 further experiments have, in some cases, only served to 

 bring to light the existence of complicating factors which 

 tend to frustrate the detection of the effect sought for, a 

 few of the experiments which were made under conditions 

 which varied over a wide range have yielded results which 

 can be considered as satisfactory evidence of the production 

 of ionization from abnormal atoms by bombardment with 

 electrons having only about 5 volts energy. 



The apparatus used in the present investigation was the 

 same as that employed in the earlier experiments, and is 

 described in detail in our paper. Its design allows of the 

 production of abnormal atoms in the main tube by the 

 ■action of radiation which enters from an auxiliary side 

 tube. In this way abnormal atoms are obtained in the main 

 tube without necessitating the presence of electrons in that 

 tube. Radiation is produced in the side tube by bombarding 

 the helium with an electron stream and passes into the main 

 tube by the process of absorption and re-emission by other 

 helium atoms, as shown in our earlier paper. Electrons and 

 any positive ions produced in the side tube are prevented by 

 the arrangement of electric fields from entering the main 

 tube and so affecting the collecting electrode. 



Having arranged for the presence of abnormal atoms in 

 the main tube, the effects of bombarding them by a stream 

 of electrons, the energy of which could be gradually in- 

 creased, were investigated with each of the arrangements of 

 electric fields designated in our earlier paper as those required 

 for the obtaining of R, and (I— R), curves, i. e , curves showing 

 the effects of radiation only, and curves in which the photo- 

 electric effect of radiation opposes the ionization current. 

 Hence, provided that in the absence of abnormal atoms the 

 variation in the measured current with variation of the 

 bombarding electron energy could be neglected, the pro- 

 duction of ionization by bombardment of abnormal atoms at 

 any given stage, would be indicated by a decrease of negative 

 current at that stage, in an R arrangement, and by either a 



