Theory of Ionization by Collision. 133 



These n x electrons cause directly by collision with mole- 

 cules N 2 (.r)f/.r ionizations in the element of space [x, x + dx), 



where 



for 3e<2l : N 2 (V) = 0, 



. . (11) 



and for #>2Z : N,(«) - Hq [x - 2/ ) (L± Y. 



The total number of the liberated electrons of the class 

 which we will denote by Class 2 is thus 



Ks - n ° 1.2 ATT/- 



Similarly, for Class v, 

 for.r<i// : N„(jb) = 0, 

 and for ,-^l : N,<*) = „ C^lf .(^ )". 

 and the total number 



i„ 



(12) 



(13) 



— (£ #(x) (14) 



Fig. 3. 



^ i «, « 44 



Fig. 3 shows an example of the distribution of the first 

 four ionization classes. 



The " centre of gravity " for the i/th class — by which we 



