-rays produced by the
-ray, it is probable that the fraction of the actual passages through helium atoms of
-rays themselves which detach both electrons is greater than the foregoing one in six. It has been estimated by Fowler at as high as three in four.
The foregoing experimental result of one in six was obtained only at the very end of the range of the
-rays where they have their maximum ionizing power. When these rays were near the beginning of their range, and therefore were moving much more rapidly, the fraction of the number of double catches to total catches was only about half as much, i.e., the chance of getting both electrons at a single shot is much smaller with a high-speed bullet than with a slow-speed one. This is to be expected if the two electrons are independent of each other, i.e., if the removal of one does not carry the other out with it.
The foregoing is, I think, the only experiment which has yet been devised in which the act of ionization is isolated and studied as an individual thing.