﻿676 Ions produced by an Alpha Particle from Polonium. 



Calculation of the Number of Ions and the Energy required 

 to produce an Ion. 



To get the number of ions produced by an alpha particle, 

 the values of the charge given to the plate " A" as recorded in 

 column 3, were divided by the corresponding values of the 

 number of alpha particles that entered the chamber, as 

 recorded in column 4, and the result divided by the value of 

 the charge of an ion, which in this case was taken as 

 4*67 x 10~ 10 electrostatic unit. The values of the number 

 of ions produced by an alpha particle, as determined in the 

 above manner, are recorded in column 5, Table II. The 

 mean of the different values found is seen to be 164,000. 



It has been shown * that the rate of production of ions by 

 an alpha particle is proportional to the rate of consumption 

 of its energy. Hence it is possible to calculate the relative 

 amount of energy that is required to produce an ion in air. 

 Taking the value of e/m for the alpha particle as 5 x 10 3 

 electromagnetic units, the initial velocity as 1*68 xlO 9 

 cm./sec, and the charge e as 3*1 x 10" 20 electromagnetic 

 unit, the kinetic energy of the alpha particle is equal to 



l/2mv 2 = l/2m/ev 2 e = 8'7 x 10" 6 erg. 



Dividing this value by the number of ions produced (164,000) 

 the relative amount of energy required to produce an ion is 

 obtained. This gives a value of 5*3 X 10 " n erg. 



Conclusions. 



The number of ions produced by an alpha particle from 

 polonium has been determined by a direct process and the 

 mean value found to be 164,000. This value is in close 

 agreement with that already found by Geiger f. 



The relative amount of energy of an alpha particle 

 required to produce an ion is calculated to be 5*3 x 10" 11 erg. 



Physics Building, University of Illinois, 

 Urbana, Illinois. 



* Geiger, Proc. Royal Society, Series A, vol. lxxxiii. No. 565, p. 505 ; 

 Taylor, Phil. Mag. April 1911. 



t Geiger, Proc. Roval Society, Series A, vol. lxxxii. pp. 486-495, 

 July 31, 1911. 



