Recombination of ions at different temperatures

Abstract

Doubts were felt about the results of McClung’s experiments on this subject very soon after he published them, and Langevin indicated the weak point in them by showing that, in the apparatus used, diffusion would have a large effect and would be responsible at the higher temperatures for most of the disappearance of the ions. The present experiment was therefore carried out under such conditions that the diffusion could be safely neglected. At the highest temperature attained it will be seen that the diffusion is probably not quite negligible, but the error even here is certainly not a very large fraction of the whole. Theory of the Method . A layer of air of uniform thickness situated between two parallel electrodes is ionised by a single flash from a Röntgen bulb. The quantity of electricity received by either electrode will depend upon the field established between them. It is easy to show that N = ( k 1 + k 2 ) X/ α log (1 + αn 0 t /( k 1 + k 2 ) X), where N is number of ions received per unit area of the electrode; k 1 and k 2 are the velocities in unit field of the positive and negative ions respectively; X is the field; α is the coefficient of recombination; n 0 is number of ions per cubic centimetre originally produced by the flash; t is thickness of the layer of air ionised.