Abstract
SIR J. J. THOMSON'S comment in the November Philosophical Magazine upon the similarity between the non-luminous layers which cover cold surfaces in a high-frequency electrodeless discharge, and the intensely dark region within the cathode dark space and immediately adjacent to the cathode of a Geissler discharge, discovered by Dr. F. W. Aston in 1907, points to a fresh way for rinding the respective contributions of positive ions and electrons to the current in the latter case. Both have the appearance of the positive ion sheaths which have recently become important through their application by Langmuir to the theory of exploring electrodes. Since there is good evidence that the fall of potential across the Aston dark space is the ionisation potential of the gas, the current density of positive ions can be calculated by inserting in Langmuir's equation for a plane collector the appropriate observed thickness of the layer, and when compared with the total current density, this will give the required information, without, of course, affording any idea as to exactly how the electrons are produced at the metal surface.
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EMELEUS, K., CARMICHAEL, N. The Aston Dark Space. Nature 121, 14 (1928). https://doi.org/10.1038/121014a0
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DOI: https://doi.org/10.1038/121014a0
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