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BELL SYSTEM TECHNICAL JOURNAL 



One instinctively compares these values with the ionizing and 

 resonance potentials of the gases, and finds them mostly lower. But 

 actually there is no sense in making such a comparison, and indeed 

 it is difficult to derive from theory anything with which they may 

 profitably be compared. The most that one can do is to attempt to 

 estimate the maximum kinetic energy which electrons should possess, 

 not after having fallen through a constant potential-drop of the stated 

 magnitude, but while they are under the influence of an oscillating 

 fieldstrength of the corresponding amplitude. 



Fig. 23 — Least maintaining-potential vs. pressure in rarefied neon at frequency 



7-10'. (Rohde.) 



The formula required was given in equation (4) of Part I, but on 

 examining it, one sees that it involves an unknowable quantity. Say 

 that the fieldstrength is directed along the axis of x, and is given by 

 the expression eE sin {lirvt), so that it is zero at / = and positive 

 immediately after; then this unknowable quantity, denoted by v^, is 

 the component along the :x;-axis of the velocity of the electron at 

 / = 0. Indeed, there is a second unknowable, the component normal 



