CjESIUm-oxygen-silver photoelectric cell 



361 



hours of deposition which is most pronounced at 7,500 A. This is 

 followed by a decay which is again most rapid for the longer wave- 

 lengths. The responses for 9,500 A. and 10,000 A. show no rise 

 and decrease steadily after 10 hours. The responses at these wave- 

 lengths were probably at their maxima initially, while the responses 

 at all shorter wave-lengths reach their maxima with increasing time 

 in the order of a progression of wave-lengths from infra-red to visible 

 light. Calculation from the constants in Table 3 shows the maximum 



4 6 8 10~3 



LAYERS OF CAESIUM DEPOSITED 

 4 6 8 10"2 2 4 6 8 10"' 



100 200 400 



HOURS OF DEPOSITION 



Fig. 15 — Spectral response changes in cell F, position 1. 



response at 7,500 A. to correspond to the deposition of approximately 

 one tenth of an atomic layer, as may be seen from the scale of abscissae 

 at the top of the figure. 



For position 2 of this same cell, where the deposition was 20 times 

 as rapid, the curves show a great similarity in every respect including 

 the proportionality of the time scales up to the point corresponding to 

 one tenth of a layer, as may be seen in Fig. 16. Then the maxima 

 spread out and the falling off of response is relatively slower than 

 that found in Fig. 15 as expressed in terms of layers deposited. In 



