Single ionization of calcium by electron impact

Relative cross sections for the single ionization of calcium were measured in the energy range from threshold to 100.7 eV using a time-of-flight ion detection method. Simultaneous detection of the ions from ionization of water molecules was used to monitor and eliminate energy-dependent effects. Present cross sections are normalized at 40 eV using previous experimental data. A comparison is made with existing partial cross sections for Ca+ as well as total ionization cross sections to highlight the significant difference which exists in the energy shape and magnitude of the cross section maximum.