ELECTRON IMPACT IONIZATION OF C$^{q+}$, N$^{q+}$ AND O$^{q+}$ IONS

F.~Scheuermann, K.~Aichele, D.~Hathiramani, M.~Steidl, M.~Westermann and E.~Salzborn

Institut f\"ur Kernphysik, Justus--Liebig--Universit\"at Giessen, D-35392 Giessen, Germany

In an animated crossed-beams experiment absolute cross sections for electron impact double ionization in 
different charge states $q$ of C$^{q+}$ (q=1-3), N$^{q+}$ (q=1-4) and O$^{q+}$ (q=1-4) ions have been measured 
for electron energies from threshold up to 5~keV. Furthermore, we have measured the electron triple ionization 
cross section of C$^{+}$, N$^{2+}$, O$^{q+}$ (q=1-3) and quadruple ionization cross section for O$^{+}$. The 
cross sections show strong indirectcontributions from the K-shell with increasing ionization degree.