End-point energies of electrons ejected during Auger neutralization of slow, multicharged ions near metal surfaces

A study has been done of the end-point energies of electrons ejected during Auger neutralization of slow, multicharged ions near metal surfaces. The study includes a wide variety of ions. Experimental results are presented for Al^z+ and Cⁿ⁺ ions incident on a gold surface, where z=2–5 and n=2–5. Ions from a laser-ion source are processed to produce ion pulses with incident energies ranging from 40 to 280 eV/charge. Data published by Hagstrum for 200-eV He²⁺, Neⁿ⁺, Arⁿ⁺, Krⁿ⁺, and Xeⁿ⁺, on tungsten, where n=2 and 3, are analyzed along with the work of Varga, Hofer, and Winter for low-energy Ne²⁺, Ar²⁺, Ar³⁺, Kr²⁺, and Xe²⁺ on tungsten. It is concluded that the high-energy end of the Auger emission is dominated by single-electron capture by the ion and an internal conversion process involving direct coupling of optically allowed transitions in the lower-lying excited states of the singly neutralized ion to the top of the conduction band of the metal target. It is shown that a considerable fraction of the neonlike Al³⁺ ions from the laser-ion source are in a metastable state and are neutralized through autoionization.