Absolute cross sections for electron-impact ionization of the rare gas atoms by the fast neutral beam method.

Despite the fundamental importance of electron impact ionization cross sections, few accurate absolute measurements have been reported. To obtain such data for reactive species such as free radicals, we have constructed a crossed electron beam- fast neutral beam apparatus. This work characterizes the apparatus by measuring rare gas atom absolute ionization cross sections and ratios of the cross sections for single-to-multiple ionization, from threshold to 200eV. The accuracy of the results is +- 15%, based on analyses of systematic errors and comparisons to previously reported values.