Charge exchange at molecular-orbital pseudocrossings as an important mechanism for nonkinetic-electron emission in slow-multicharged-ion (v<v0) metal-surface scattering

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Abstract
Kinetic energy distributions of electrons emitted in the interaction of slow (10q-keV) multicharged ions (N,O,Ne,Ar) with metal surfaces (Cu,Au) are presented. We observe secondary-electron emission, quasielastic-scattering processes, and, superimposed upon this, one-center Auger decay of both projectile and target vacancies. Two classes of target Auger-decay features are observed. Long-lived target vacancies decay, leading to discrete Auger line features, similar to those arising from electron-impact excitation. Short-lived target vacancies appear to decay in the field of the projectile, leading to broadened Auger line features. Observation of the decay of target vacancies, and their correlation with the presence of particular projectile vacancies, shows that a measurable fraction of projectile vacancies survive until small-impact-parameter collisions with surface or subsurface atoms. The data imply that projectile neutralization proceeds via two channels, viz., capture of valence-band electrons to projectile excited states, followed by one-center Auger decay, and at pseudocrossings of molecular orbitals correlating with discrete inner-shell levels of the target and projectile.

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