Inelastic collisions between electrons and noble gas ions

The excitation of the lower levels of noble gas ions and dielectron recombination of the helium ion are investigated systematically using intersecting modulated electron and ion beams. The energy dependences of the effective excitation cross sections are analyzed, and their absolute values are determined for 32 spectral transitions. Well defined structure maxima are identified in the cross sections of the processes studied, with most of the maxima being of resonance nature. It is shown that the resonance maxima result from the formation and decay of autoionization states of neutral atoms.