ELECTRON-IMPACT MULTIPLE IONIZATION OF SINGLY AND MULTIPLY-CHARGED TUNGSTEN IONS

Cross sections for electron-impact double ionization of W-q+ ions in c harge states q = 1-6 as well as triple ionization in charge states q = 1-4 have been measured using the crossed-beams technique. A new semie mpirical formula for multiple ionization of three or more target elect rons is in very good agreement with the measurements. Together with pr eviously obtained experimental data for single ionization of tungsten ions, the measured cross sections are used to study the influence of m ultiple ionization on the W-q+ charge state evolution if tungsten atom s are exposed to an electron Bur at 700 eV energy. It is shown that th e charge state evolution is significantly influenced by multiple-ioniz ation processes.