| Abstract: | The experiments of several previous investigators were repeated in substance with apparatus designed to make it possible to distinguish between ionization and certain spurious factors which have made questionable much of the existing evidence relating to ionization by positive-ion impact. A great many current-potential measurements and curves were obtained at different gas pressures and with a variety of electrical arrangements. The data and curves thus obtained present direct evidence (a) that the previously so-called “ionization current” is due to a secondary electron emission from the platinum walls of the ionization chamber, (b) that this secondary electron emission is produced by the impact of the positive ions with these metal walls, (c) that either there is no ionization in hydrogen gas by the impact of the positive ions accelerated by potential differences up to 925 volts, or that if this phenomenon exists, as is indicated by visual and spectroscopic evidence, its effects are so small at relatively low pressures (.012 mm.) that it is completely masked by secondary phenomena which make its detection by the ordinary direct methods problematic, and (d) that it seems possible that at relatively high gas pressures (considerably above .012 mm.), ionization by positive ions might be an important factor with accelerating potential differences between the ends of their M.F.P. well within this same range of voltages. |
