THE 



AMERICAN JOURNAL OF SCIENCE 



[FOURTH SERIES.] 



Art. XXiy. — On the Nature of the Ionization Produced hy 

 a Mays ; * by Frank E. Wheelock. 



[Contributions from the Sloane Physical Laboratory of Yale University.] 



When a gas is ionized by a rays, it is well known that satu- 

 ration is obtained only when a large potential gradient is 

 applied between the plates of the ionization chamber. This is 

 much larger than would be necessary if the lack of saturation 

 were due to general recombination of the positive and negative 

 ions formed, if they are distributed throughout the volume of 

 the gas. 



Bragg and Kleemanf have explained the lack of saturation 

 experimentally obtained, on the hypothesis of '' Initial Kecom- 

 bination" ; the two ions made by corpuscular dissociation of a 

 molecule, situated initially in the immediate vicinity of each other, 

 are able to recombine and thus escape the electrode placed to 

 I'eceive them. On this hypothesis, lack of saturation would 

 depend upon the number of ions formed per c.c. in a unit of 

 time ; it would be independent of the size and shape of the 

 ionization chamber ; saturation would be easier with dimin- 

 ished pressure, and " Initial Recombination " would be greater 

 in the more complex gases. 



The experiments of Bragg and Kleeman show the above 

 facts and " Initial Recombination " seem to be a reasonable 

 explanation of the lack of saturation at low voltages. 



Kleeman;}: has shown that "Initial Recombination" is prac- 

 tically absent in air ionized by X rays and is very small in gases 



* A Thesis presented for the degree of Doctor of Philosophy at Yale 

 University, June, 1910. 



f On the Recombination of Ions in Air and other Gases, Phil. Mag., xi, 1906. 



:]; Recombination of Ions, made bv a, j3, and y rays, Phil. Mag., xii, p. 373, 

 1906. 



Am. Jour. Sci. — Fourth Series, Vol. XXX, No. 178. — October, 1910. 

 16 



