Resonance phenomena in inelastic interactions between slow electrons and alkali metal ions

Vacuum ultraviolet radiation arising in elastic interactions between 8 to 400 eV electrons and alkali metal ions are investigated for the first time. The effective excitation cross sections are determined for 21 spectral lines. A strongly pronounced structure of the energy dependence is observed and studied in detail, most of the peaks being of a resonance nature. The data can be explained by assuming capture of the incident electrons with the formation of autoionizing states of the atoms or ions. Subsequent decay of the states leads to a strong selective population of resonance levels of the ions, to dielectron recombination radiation emission in a narrow energy gap and, finally, to the emission of ultra-soft X-rays