66 Dr. Tate and Dr. Foote on Resonance and Ionization 



The present paper is an account of an experimental deter- 

 mination of the resonance and ionization potentials for 

 electrons in cadmium, sodium, potassium, and zinc vapours. 

 The results for cadmium and sodium have been published 

 elsewhere*, but are included here for the sake of 

 completeness. 



Fio-.]. 



To ~Pu. 



Diagram of Apparatus. 



The method employed was that of Franck and Hertzf for 

 determining the resonance potentials with the modification 

 described by Tate| for determining the ionization potentials 

 and initial potentials. The arrangement of apparatus is 

 shown in fig. 1. The metal was vaporized at the bottom of a 

 pyrex glass or glazed porcelain tube, and the vapour, after 



* Tate and Foote : Sodium, J. Wash. Acad. Sci. vii. p. 517 (1917) ; 

 Cadmium, Bulletin Bu. Standards, 1918 (in press)., 

 t Verh. d. Phys. Oes. xvi. pp. 457-467 (1914). 

 t Tate, Phys. Rev. vii. p. 686 (1916) ; idem, x. p. 81 (1917). 



