The Recombination of Ions and of Ions and Electrons in Gases

Abstract

Coefficient of recombination of ions, produced by x-rays, as function of x-ray exposure time, initial ion concentration and time of recombination.—The present work constitutes a study of the recombination of ions and of ions and electrons in gases, by means of a new direct method, using constant radiation from a Coolidge x-ray tube as the ionizing agent, together with a rotating commutator shutter. This method permits wide limits of independent variation of: (1) x-ray exposure ($t^{\prime }$); (2) initial ion concentration ($n_0$); (3) time of recombination ($t$). Results in air show that $\alpha$, previously assumed constant and equal to 1.6×${10}^{-6\mathrm{}}$ actually varies as a function of $t^{\prime }$ and of $t$. It is high, 4×${10}^{-6\mathrm{}}$ or more, for small values of the above quantities and drops rapidly to nearly a constant value. $\alpha$ is also found to be a function of $n_0$. These facts can only be explained on the assumption that the ions are not initially uniformly distributed, but are in pairs along the paths of the x-rays. This leads to fictitiously high calculated values of $\alpha$ corresponding to low apparent values of $n_0$ and $n$, erroneously computed on the assumption of random distribution. As $t^{\prime }$, and with it $n_0$ and also $t$, increase, $\alpha$ approaches a constant value between 0.8 and 0.9×${10}^{-6\mathrm{}}$, which is probably nearly the true value. This result lends strong support to the theory of Thomson that the process of diffusion plays the major role in the initial stages of the mechanism of recombination; i.e. in bringing ions together.