Excited-Atom Deexcitation Spectroscopy using Incident Ions

Outside a surface of sufficiently low work function, incident 10-eV ${\mathrm{He}}^{+}$ ions convert to excited atoms which, in turn, eject electrons in the process of Auger deexcitation (Penning ionization). The electron spectroscopy thus demonstrated for ${\mathrm{He}}^{+}$ incident on Ni(100) with adsorbed ${\mathrm{K}}^{+}$ is the essential equivalent of that employing incident metastable atoms. Energy and wave-function considerations governing the partition between neutralization and deexcitation processes are discussed and evidence of the surface sensitivity of these processes is presented.