360 



BELL SYSTEM TECHNICAL JOURNAL 



approximately four to correct for the increase in surface on roughening, 

 but it seems preferable to present the experimental results in terms 

 of measured rather than estimated quantities, so numbers of layers 

 of caesium deposited will be presented as upon a smooth surface. 



In cell E, which had the largest orifice, the changes were so rapid 

 that only one position could be followed. In Fig. 14 the response at 

 each wave-length is plotted against the time on a logarithmic scale. 



LAYERS OF CAESIUM DEPOSITED 

 4 6 8 10"' 2 46810 2 46 610 



2 70 



1MIN. 2MIN. 5 WIN J- HR -1 1 2 3 



4 2 



HOURS OF DEPOSITION 



Fig. 14 — Spectral response changes in cell E. 



The response decreased at all wave-lengths, but the effect increased 

 progressively with increasing wave-length. After two hours^ the 

 wave-length of maximum response had shifted from 7,750 A. to 

 6,000 A. 



With slower rates of deposition, initial effects become apparent. 

 In Fig. 15 are shown the results for position 1 of cell F which involved 

 the slowest rate of deposition. For wave-lengths shorter than 9,000 A. 

 there is first a rise in response to a maximum at between 10 and 20 



