Observation of surface to bulk interatomic Auger decay from Ta(100)

Core-valence-valence (CVV) Auger spectra from Ta(100) taken in coincidence with bulk and surface-shifted 4f7/2 core-level emission are presented. These data are compared with self-convolutions of calculations of the d-band densities of states for the surface and subsurface layers of a nine-layer slab. Agreement of the bulk spectrum with the calculation is good; agreement for the surface spectrum is very poor. These data are explained by proposing an interatomic surface to bulk Auger decay mode for the surface core hole that is competitive with the conventional CVV decay process.