﻿29 (J Recombination of Ions made by a, /3, 7, and X Raijs. 



the ejected electrons being smaller the smaller the velocity 

 or' the a particles. The electrons are very likely ejected at 

 right angles to the motion o£ the a particles. And we know 

 that the electric force at right angles to a moving electric 

 charge is greater the greater the velocity of the charge. 



*The range of the a particle of polonium determined by 

 this apparatus was found to be 3*80 cms. at a pressure of 

 77*34 cms. of mercury and a temperature of 12° C. 



The range was obtained from the curve K, in which the 

 leaks were plotted against distances of polonium film to the 

 side of gauze nearest the electrode. 



§VI. 



Summarizing the results recorded in this paper we have: — 



1. The lack of saturation with weak ionization by a rays 



is not due to diffusion of ions, nor does it depend on 

 the recombination coefficient or velocity of the ions. 



2. Initial recombination is very small in gases ionized by 



ft, 7, or X ra}^s; in other words, these ionizing agents 

 effect a complete separation of the negative ions from 

 their parent molecules. 



This appears to be related to the fact that the 

 secondary cathode rays from a metal plate on which 

 /3, 7, or X rays fall, have considerable penetrating 

 power, while no such penetrating cathode rays have 

 been shown to exist in the case of the a particle. 

 And it seems reasonable to conclude, from this and 

 other facts, that the velocities of the electrons ejected 

 from molecules in the gaseous state ionized by /3, 7, 

 or X rays are of the same order, while the velocity of 

 an electron ejected by an a particle is much smaller. 



3. This property of the /3 rays is not destroyed by passing 



them through a thick aluminium plate. 



4. The initial recombination observed when a gas is simul- 



taneously ionized by a and 7 rays is equal to their 

 separate effects. 



5. Initial recombination is greater the slower the velocity 



of the ionizing a. particle, which probably means that 

 the slower the velocity of the a particle the slower the 

 velocity of the ejected electrons. 



* Before the publication of this work a paper appeared in the Phys. 

 Zeit., May 1906, by Kucera and Masek, who describe some experiments 

 having the object of finding the range of the a particle of polonium and 

 the ionization along its course. These experimenters make the range 

 4*1 cms. (measured from gauze) at a pressure of 73*3 cms. of mercury. 

 Allowing for the greater atmospheric pressure in my experiment, my 

 range is slightly lower than theirs. 



