SINGLE AND MULTIPLE IONIZATION OF NI-Q-IMPACT( IONS BY ELECTRON)

Employing the crossed-beams technique, absolute cross sections for ele ctron impact single ionization of Ni-q+ ions in charge states q = 2-5 have been measured for energies from threshold to 1000 eV. The Ni2+ an d Ni3+ results show a significant ionization signal below the,around s tate threshold due to substantial components of metastable ions in the parent ion beams. In the case of Ni4+ and Ni5+, no significant contri butions of metastable ions to the measured cross sections have been fo und. The results are in reasonable agreement with theoretical calculat ions. For the first time we have measured absolute cross sections for electron impact double ionization of Ni-q+ ions in charge states q = 2 , 3, 4.