Emission of Soft Electromagnetic Radiation from Metals by the Impact of High-Energy Protons and Positive Ions

Abstract

IT is known that the impact of fast protons1 and α-particles2 on metals results in the emission of their characteristic X-radiation. It has not been reported, however, whether ultra-violet and visible radiation are also emitted from metals when high-energy protons and positive ions strike them. Sir J. J. Thomson3 predicted as early as 1914 that the impact of positive ions on metals may result in the emission of soft electromagnetic radiations. Evidence supporting this view has been given in recent experiments, where it is shown that ultra-violet and visible radiation is emitted when positive ions and protons of moderate energies strike a nickel surface4. These experiments have now been extended to protons and positive ions of energies of 400–700 keV.