256 Taylor — Ionization of Gases by the Alpha Particles. 



Results. 



1. The ionization curve obtained in various gases and 

 vapors with polonium as the source of rays is of the general 

 form 



(r—x) 



where 7" is the ionization ; c is a constant for any one gas 

 depending upon the total ionization produced, and conse- 

 quently upon the energy required to produce an ion in the 

 given gas ; r is the average range of the alpha particles in the 

 cone of rays ; and x is the distance from the source of rays. 



2. The agreement between the theoretical and the experi- 

 mental curves confirms the assumption made in previous papers 

 by the writer* and by Geiger,f that the ionization produced by 

 the alpha particle is proportional to the energy consumed. 



3. The values of the ratio of the total ionization produced 

 by the alpha particle in different gases to the total ionization 

 produced in air as found by Bragg have been confirmed by a 

 more direct process. 



4. The energy of the alpha particle consumed in the pro- 

 duction of an ion depends upon the nature of the molecule 

 ionized. It apparently requires less energy to produce an ion 

 in the gases or vapors which have heavy or relatively complex 

 molecules than it does in those gases of lighter or less complex 

 molecules. 



Laboratory of Physics, University of Illinois, 

 Urbana, Illinois, January 28, 1911. 



* Loc cit. f Loc cit. 



