Electron diffusion,electron attachment,and the aging of negative ions in commercial nitrogen at atmospheric pressure

A criticism by Loeb and Bradbury of my interpretation of the experimental results of that part of a previous paper which dealt with the aging of negative ions in commercial nitrogen is shown to be invalidated by a mistake in their analysis and by assumptions which do not represent facts with sufficient accuracy. A more extended analysis of the previous work and new evidence which is given confirm the correctness of the former contention that the negative ions in question changed in size with age. The lateral spread, owing to diffusion, of a stream of electrons in this nitrogen at atmospheric pressure, when moving in an electric field of about 100 volts/cm., was found to be very nearly the same as that for positive ions under like conditions. The average energy losses of the electrons at collision with the molecules must therefore have nearly balanced the gains from the electric field and hence were greater than would result from purely elastic collisions. The experimental results indicate that in fields down to at least 20 volts/cm. nearly all of the attachment of electrons to molecules in the gas used occurred close to the place of their liberation.