﻿T H E 

 LONDON, EDINBURGH, and DUBLIN 



PHILOSOPHICAL MAGAZINE 



AND 



JOURNAL OF SCIENCE. 



[SIXTH SERIES.] 



APRIL 1912. 



XLII. Ionization by Moving Electrified Particles. 

 By Sir J. J. Thomson'*. 



THE theory developed in this paper is based on the 

 following assumptions : — 



1. Cathode or positive rays when they pass through an 



atom repel or attract the corpuscles in it and thereby 

 give to them kinetic energy. 



2. When the energy imparted to a corpuscle is greater 



than a certain definite value — the value required to 

 ionize the atom — a corpuscle escapes from the atom, 

 and a free corpuscle and positively charged atom are 

 produced. 



We must first find under what circumstances a cathode 

 ray moving with a given velocity will lose when it passes by 

 a corpuscle a quantity of energy greater than the amount 

 required to ionize an atom. 



In my ' Conduction of Electricity through Gases ' it is 

 shown that when a body with a charge Ei in electrostatic 

 units and mass M. x is projected with a velocity V towards a 

 body with a charge E 2 and mass M 2 at rest, tho energy Q 

 transferred to the latter is given by the equation 



n 4M T M 2 T . 2/) 

 Q= (M 1 + M 2 )* Tsm *' 



* Communicated by the Author. 



Phil. Mag. S. 6. Vol 23. No. 136. April 1912. 2 II 



