NE-STAR-STAR AUTOIONIZING STATES AND NE+ CHARGE FRACTIONS SCATTERED FROM A MAGNESIUM SURFACE

The first correlation of autoionization, inelastic energy loss, and charge fractions for ions scattered from surfaces is reported. A mechanism for efficient ionization of atoms receding from surfaces has been identified and confirmed. It involves the formation of an autoionizing atom which, due to its long lifetime, ionizes far from the surface where reneutralization is unlikely. This is exemplified by keV Ne+ on a Mg surface, where a fraction of the Ne+ can be doubly excited to Ne**(2p43s2) states when the interatomic distance is 0.6 s/rA.. The behavior is described by electron promotion and by fast electron transfer with the solid. © 1990 The American Physical Society.