Regensburg 2013 – scientific programme

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O: Fachverband Oberflächenphysik

O 35: Poster Session I (Metal, semiconductor and oxide substrates: structure and adsorbates; Graphene)

O 35.2: Poster

Tuesday, March 12, 2013, 18:15–21:45, Poster B1

Electron pair emission from surfaces upon He²⁺ impact — •Chang-Hui Li¹, Christian Tusche¹, Frank O. Schumann¹, and Jürgen Kirschner^1,2 — ¹Max-Planck-Institut für Mikrostrukturphysik, Weinberg 2, 06120 Halle — ²Institut für Physik, Martin-Luther-Universität Halle-Wittenberg, 06099 Halle, Germany

Using a two-electron coincidence spectrometer, we have studied the electron pair emission upon the impact of 10 eV normal incident He²⁺ ions on Ir(100) and Fe(100)-p(1×1)O surfaces. According to the commonly used two-step model [1], He²⁺ is firstly converted to He⁺ and then to He⁰. Two electrons are emitted incoherently by the two corresponding neutralization steps. As the ionization potentials of He²⁺ → He⁺ and He⁺ → He⁰ are 54.4 eV and 24.6 eV, respectively, a very unequal energy sharing is expected. In the two-electron coincidence spectra, the dominant events can be understood by the incoherent two-step mode, but we have found clear evidence that this approximation breaks down and the neutralization should be treated as a single process.