﻿Low-Speed Positive H-Ions in Hydrogen, 



821 



" cross-over " potential is shown in tier. 5 at 25 volts. The 

 effect of increasing the thermionic current and so the posi- 

 tive ionizing current is to shift the graph along to the right 

 so that the cross-over potential is increased. These facts 

 can be explained readily by the fact that the incoming 

 positive ions ionize by collision. The current to E is thus 

 made up of two currents — the positive ionizing current and 

 the negative current of the negative ions produced. When z 

 is sufficiently large, this negative electron current is sufficient 



Fiff. 5. 



•400 



+300 



+ 200 



100 



-iOO 











Hydr 



open. 



P ■'■' 



mm. 















x = 30 



Total 



v. 

 Accel 



y=4v. 



eratin 



9 PD 



V=l8v. 

 34 vo 



Its. 









































i. 































































-5 



+ 5 10 15 20 25 30 31 



Total retarding Field (Z vcits) 



40 



45 



to swamp the positive current retarded by z and by collision 

 with the gas molecules. In this manner definite evidence of 

 ionization by positive ions accelerated through potentials as low 

 as 18 volts has been obtained. 



Other ionization tests were carried out with the retarding 

 potential z of constant value and greater than the minimum 

 value of x+y, the total accelerating P.D. Table I. illus- 

 trates the relation between the positive ionizing current 

 and the negative ionization current for different applied 

 P.D's. 



