Use of spin-labelling techniques to probe the dynamics of He(23 S) deexcitation at solid surfaces

Spin labelling techniques, specifically the use of electron-spin-polarized He(2³ S) metastable atoms coupled with energy-resolved spin analysis of the ejected electrons, are used to investigate the dynamics of He(2³ S) deexcitation at solid surfaces. Data for a clean Au(100) surface are presented that show that deexcitation occurs exclusively through resonance ionization followed by Auger neutralization. The electrons involved in Auger neutralization are observed to be correlated in spin and possible reasons for this are discussed. Results obtained at Xe and NO films adsorbed on cooled Au(100) and Cu(100) substrates, respectively, show that He(2³ S) metastable atom deexcitation is analogous to gas-phase Penning ionization. Detailed differences are apparent that can be attributed to effects associated with the underlying substrate and interactions involving neighboring atoms in the film.