The ionization of xenon(nf) Rydberg atom at a metal surface

A thermal-energy beam of Xe(nf) Rydberg atom has been utilized to study electron tunneling during atom/surface interactions. The Xe Rydberg atoms, which are created by laser-induced photoexcitation of Xe(3P 0) metastable atoms, are incident at near grazing angle on a flat Au(1 1 1) surface. At some critical distance, the Rydberg electron will tunnel into a vacant level in the Au surface The resulting ions are observed by applying a pulsed collection field which is big enough to overcome the image charge of the product ions. Measurement of the ion signal as a function of the applied field gives the threshold field which depends critically on the atom/surface separation at which ionization occurs. Analysis of the data for the current range of (13 ≤ n ≤ 20)n provides results in good agreement with first-principles complex scaling calculations that employ accurate atom-surface interaction potentials. Measurements show that the ionization distance depends critically on the flatness of the surface. Surprisingly, measurements using red and blue Stark states yield quite similar ionization distances and this is being investigated theoretically