Untersuchung über die Emission positiver Sekundärionen und die Reflexion von Edelgasionen an Festkörperoberflächen

Abstract

Rare gas ions He+, Ne+, Ar+, Kr+ and Xe+, the energy of which could be continuously varied between 100 and 30 000 eV, were produced in an electron impact ion source, and focussed on a target. The secondary target ions were measured. A portion of the secondary ions was analysed in a parabola spectrograph according to their masses and energies. The yield of positive secondary ions of graphite, copper, and gold targets increases slowly with increasing primary energies, starting at 4 keV. It further shows a systematic dependence on primary ion mass. The results are described by an empirical formula. At a primary energy between 1 and 2 keV the yield curves show a maximum, the heighth of which depends on the previous treatment of the target. The target materials graphite, aluminium, iron, copper, silver, tantalum, tungsten, platinum, and gold were investigated with the parabola spectrograph. The spectra, detected on a photographic plate, consist 1) of the mass spectrum of the secondary ions from the target material and of the ions resulting from surface contaminations and 2) of the spectrum of reflected rare gas ions. The ions of type 1) appear at an energy value corresponding to the post-acceleration of the parabola spectrograph. The reflected rare gas ions which were monoenergetic prior to reflection blacken a sharply defined portion of the parabola which increases in length with decreasing mass of primary ions m1 and increasing mass of target atoms m2. If the masses of the rare gas ions exceeded that of the target material, no reflected ions could be observed. A sharp intensity maximum is superimposed on that portion of the parabola which is due to the reflected rare gas ions. The position of this intensity maximum exhibits a systematic change with regard to the end portions of the parabola with the mass number of both reflected ions and target atoms.