白金単結晶表面に吸着した希ガス(Ar, Kr)の電子衝撃脱離

抄録

Electron-stimulated desorption of argon and krypton adsorbed on Pt (111) was studied for the electron energy range from 10 to 120 eV. The ion species investigated were Ar⁺, Ar₂⁺, Ar²⁺ for argon, and Kr⁺ for krypton. The threshold energy for Ar²⁺ desorption was found to be 83 eV, which is interpreted in terms of the formation of Ar³⁺ followed by the Coulomb repulsion of two adjacent ions produced by the curve crossing from Ar³⁺ Ar to Ar²⁺ Ar⁺ or Ar^2+* Ar⁺. For the desorption of Ar⁺ and Ar₂⁺, resonant excitations with onsets at 24.2, 25.4, 34, and 50 eV have been found. The first two thresholds are interpreted as pairs of interacting surface and bulk excitons, respectively. The details of the desorption mechanism are discussed in connection with the threshold energies and the thickness dependences of desorption intensities.