C^SIUM-OXYGEN-SILVER PHOTOELECTRIC CELL 



365 



In Fig. 19 are shown spectral distribution curves of the response to 

 equal energy with different amounts of deposited caesium selected 

 from the data shown in Fig. 15. These curves show in more con- 

 ventional fashion the shift in the position and height of the spectral 

 maximum. This illustrates the general behavior of the equilibrium 

 surface upon the addition of further caesium. There is an increase in 

 response at the spectral maximum upon the addition of approximately 



80 



6000 



7000 



9000 



10000 



8000 

 WAVELENGTH IN A 



Fig. 19 — Relative spectral response to equal energy for cell F, position 1. 



one tenth of a layer of caesium. As further caesium is added the 

 height of the spectral maximum progressively decreases. The wave- 

 length of the maximum spectral response and the wave-length of the 

 photoelectric threshold both recede progressively toward the ultra- 

 violet upon the addition of free caesium to the normal surface. 



Combining the results from the experiments where oxygen was 

 admitted to the cells and those where additional caesium was deposited 

 upon the cathode, we have a sequence of states with increasing thick- 

 ness of the caesium thin film upon the cathode surface. If we take 



