Ar L-shell ionization by electrons and light ions: determination of X-ray emission cross sections and mean fluorescence yields for charge-state distributions

Abstract

The absolute cross sections for ArL_2.3 X-ray emission have been measured for 0.25-14 keV electrons, 30-500 keV protons, 30-150 keV H₂⁺, 30-800 keV He⁺, and 600-2000 keV alpha particles, incident on argon gas. Experimental problems associated with absolute measurements of the X-ray cross sections, particularly the detection efficiency, are discussed. In order to calculate mean fluorescence yields the X-ray data have been compared with available L_2.3 Auger-electron-ejection cross sections; the accuracy of the absolute fluorescence yields obtained is about 37%. An extensive analysis is presented on the outer-shell charged-state distributions of the Ar L ions formed, considering the fraction of normal Auger transitions, the different types of excitation mechanisms and some empirical models.