566 Prof. K. T. Compton on Ionization and Production 



subtracting- the corresponding values of E for zero pressure, 

 allowance being made for the difference in total currents I in 

 the respective cases. 



If ionization between 20'2 and 25*5 volts is to be ascribed 

 to the combined effect of radiant energy and energy of 

 impacts, it is to be expected that, as the thermionic current 

 I is increased, the amount of ionization should increase 

 relatively more rapidly than the amount of radiation. That 

 this is true is shown by fig. 7. The rate of variation of R 

 with I, however, is not as great as might be expected. 



Fig. 7. p=0T5 mm. ; Curve 1, I 20 = (H5 (10) " 6 amp. ; 

 Curve 2, T 20 = 1-5 (10)~ G amp. 



1.60 



1.40 



R 



1.20 



1.00 



































. 



. 



6 



\ 



















• 











'V 













\ 



^s 



1 



























2^ 



Vn. 



































































































20 



22 



24 



26 w , 28 ^ 

 Va (Volts) 



30 32 



H The curves of figs. 2, 3, 4, and 7 show a fairly constant 

 value of R between 20*2 and 25*5 volts. This is not generally 

 the case, however. Owing to the increasing values of I as 

 V a is increased, the value of R tends to diminish. On the 

 other hand, owing to the increased proportion of the effective 

 collisions which occur on the filament side of the gauze G as 

 Y a is increased, the proportion of ionization (as measured 

 by E) tends to decrease, and consequently the value of R to 

 increase. Neither of these variations is very large, and it 

 was always possible to find a value of I at which they practi- 

 cally neutralized each other. Table I. is based on values of R 

 taken from such cases where R remained practically uniform 

 within the specified range. 



An attempt was made to express analytically the proportion 

 i/r to be expected on the theoretical grounds outlined above, 

 but there are too many uncertain factors to make a satis- 

 factory analysis possible. There are involved the coefficient 

 of absorption of the resonance radiation in the gas, the time 

 during which radiant energy of impact is retained by an 

 atom, the probability of ionization or inelastic impact at 



