46 



THE THEORY OF IONIZATION OF GASES 



shown from the results that have been obtained that 

 positive ions are much less efficient than negative ions 

 in producing new ions by collision even when they have 

 the same kinetic energy. For, assuming that the 

 positive ions are large compared with negative ions and 

 of the same order of magnitude as the molecules of the 



/ 



OS 



C4 

 03 

 ^ 



01 



100 200 boo loo $00 <MO 



foo 



900 **oo loco 1100 ieoo isoo 



(X in volts per centimetre, p in millimetres of mercury.) 

 Figure 9. 



gas from which they are derived, each positive ion would 

 make four times as many collisions with molecules as a 

 negative ion in travelling the same distance in the gas. 

 The free paths of a negative ion in a gas at pressure p 

 will therefore be the same as the free paths of a positive 

 ion in a gas at pressured/4, and if the same electric force 



