Abstract
IN the issue of NATURE for December 19, p. 900, Dr. A. J. Dempster states that he has found that slowly moving protons pass almost freely through helium atoms without being neutralised. In this connexion it may be of interest to state that I have found in the course of experiments on the scattering of protons (hydrogen positive rays) by helium and other gases, that the scattering in helium is a maximum for rays of the energy of about 10,000 volts. For slower rays the scattering is less, and for rays of 3500 volts, the slowest examined, is about 75 per cent, of the maximum. While these rays are considerably faster than those used by Dempster (300 to 900 volts), both results are probably part of the same effect. This may be analogous to the abnormal penetration of very slow electrons through certain gases found by Ramsauer. The velocities of these electrons were about the same as those of the protons used by Dr. Dempster. The effect was most marked in argon, but also occurred in helium and neon.
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THOMSON, G. The Free Path of Slow Protons in Helium. Nature 117, 235 (1926). https://doi.org/10.1038/117235b0
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DOI: https://doi.org/10.1038/117235b0
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