Correlated Electron Dynamics at Surfaces Investigated via He2+ Ion Neutralization

Abstract

The neutralization of a single He^{2+} ion near a Ir surface leads to the emission of an electron pair. Via coincidence spectroscopy we give evidence that a sizable amount of these electron pairs originate from a correlated single step neutralization of the ion involving a total of four electrons from the metal. These correlated electron pairs cannot be explained in the common picture of two consecutive and independent neutralization steps. We infer a characteristic time scale for the correlated electron dynamics in the metal of 40-400 as.

Negative ion formation by neutral hydrogen atom grazing scattering from a LiF(100) surface

“…25,25] keV (ref. 28) studied here (the plausible of the choosing of this surface altitude range can be seen by: (i) the Z˛ [2,3] a.u. range, measured from the last atomic plane, is representative of the turning point of the trajectory in grazing-angle experiments with a perpendicular energy in the eV range; 26,32,33 (ii) the range of projectile trajectory turning point of F-MgO(100) 20 and F-LiF(100)/KI(100) 28 collision systems are respectively Z˛ [1.8, 3] a.u.…”

“…Charged particle-surface interactions as an important eld have been intensively researched over several decades. Most studies have focused on, for instance, ion-or electron-induced sputtering and desorption, 1 ion stimulated surface electron emission, [2][3][4] energy loss, 5 and ion induced surface nanostructures. [6][7][8][9] The charge state in scattered beams aer projectile scattering from an insulator ionic-crystal surface has received much attention.…”

Imaging Momentum–Space Two‐Particle Correlations at Surfaces

“…[37,38] A modified sputter ion gun allowed the excitation of the surface with low-energy He þ and He 2þ ions. [39][40][41] Studies on Auger decay were conducted at the synchrotron light source BESSY II of the Helmholtz-Zentrum Berlin (HZB). We comment briefly on a new DPE setup which uses a light source based on high harmonics generation in combination with a pair of time-of-flight spectrometers.…”

“…However, a cutoff value where the intensity drops sharply cannot be identified. [41] A closer look at the intensity levels of Figure 12a reveals that outside the L-shaped region only 2% of the total intensity is Figure 11. Neutralization step via Auger capture of a singly charged ion in the vicinity of a metal surface.…”

“…It turns out that He 2þ neutralization is accompanied by the electron-pair emission which is by no means a trivial point. [41] In Figure 12 we show the 2D energy distribution obtained from a Ir(100) surface with an incoming He 2þ beam of 10 eV kinetic energy. An L-shaped region is defined by the red boundaries.…”