246 



Mr. K. F. Nesturch on Ionization and 



an electron has gained an amount o£ energy, sufficiently great 

 to be able to ionize, it must sometimes pass a considerable 

 distance before it comes into collision with a gas molecule. 

 We can make the probable assumption that, when such an 

 electron overcharged with energy collides with a gas molecule, 

 the electron newly formed by the process will have the 

 initial velocity at the expense of the excess of energy of the 

 parent electron. Therefore it will be further moved as if it 

 were formed right on the plane, parallel to the cathode plate, 

 where the parent electron had acquired the critical amount 

 of energy sufficient for ionization. The movement of the 

 latter, however, will be slower when compared with that 

 assumed in the simplified calculations of the expression (1). 



Consequently for large values of X, the charge received by 

 the anode and therefore the values of a are less than those 

 calculated by means of the expression (1) and formula (4). 

 As stated by Prof. Townsend*, the highest possible value of 

 a does not depend upon X, and is equal to the number of 

 free paths of the electron per centimetre of its way. 



Therefore one might expect that the lines, representing a 

 as a function of X for large values of X, will become more 

 and more concave towards the axis of abscissse. Further, 

 since according to the formula (4) these lines ought to pass 

 through the origin, they will have the form represented in 

 fig.l. 



Fig. 1. 



Fig. 2. 



■ 2£ 



P 



Experimental curves, however, have the shape given in 



fig. 2, and this shows that - is a linear function onlv for 



X P 



certain values of — . 

 p 



Such disagreement may be due to different causes. Either 



L.c. 



