Multielectron neutralization channels in ion-surface scattering

Effects of the atomic level shift in the Auger neutralization rates of noble metal surfaces

In this work we compare characteristics of Auger neutralization of [Formula: see text] ions at noble metal and free-electron metal surfaces. For noble metals, we find that the position of the energy level of He with respect to the Fermi level has a non-negligible influence on the values of the calculated Auger rates through the evaluation of the surface dielectric susceptibility. We conclude that even though our calculated rates are accurate, further theoretical effort is needed to obtain realistic values of the energy level of He in front of these surfaces.

Role of d electrons in Auger neutralization at metal surfaces

A generalized theory of Auger electron transfer processes in the interaction of ions with metal surfaces, including the previously ignored role of d electrons is presented. It is shown that a correct and accurate description of Auger neutralization has to account for the contribution of d electrons, as this is illustrated on the case of He+ ion neutralization on Ag, where the neglect of these leads to a strong overestimation of ion survival probabilities. Crystal lattice site specific rates are calculated and allow for a correct description of crystal azimuthal effects in neutralization.

Calculation of transition probability for neutralization process of +1 ion based on the Noziéres and Dominicis theory

We investigate the neutralization probability of a +1 ion moving parallel to a metal surface, mainly using the Noziéres and Dominicis theory (ND theory), which was applied to the edge singularities in x-ray absorption and emission spectra in metals. In particular, we focus on the effects due to the sudden disappearance of the image potential in the neutralization process. From the analysis, we found that the neutralization probability is given by [Formula: see text], where D and Γ are the band width and the gamma function. The factor α = 2δ/π-(δ/π)(2) is given by the phase shift (δ: phase shift on Fermi surface), and the energy difference between the initial and final states, Δ, includes the kinetic energy of the ion and various other phenomenological factors. The singularity caused from the sudden disappearance of the image potential enhances or reduces the neutralization probability depending on the symmetry of atomic orbital of the ion. When the ion velocity is too fast to form an image potential, the neutralization process would proceed without the creation of an image potential, accompanying an excitation of a surface plasmon; as a result of plasmon excitation the ion velocity becomes slower than the plasma frequency because of screening effects. In this paper, we apply the ND theory to the case of slow ion motion and discuss the dynamics.

Evidence for F(-) formation by simultaneous double-electron capture during scattering of F(+) from a LiF(001) surface

Slow F(+) ions (v<0.1 a.u.) scattered from a clean and flat LiF(001) surface under a grazing angle of incidence exhibit a high probability for forming F(-) ions in the reflected beam, whereas no negative ions are found for neutral F(0) projectiles. From detailed studies of projectile energy loss and charge transfer, we find evidence for a correlated double-electron capture process in the formation of the F(-) ions.

Electron bihole complex formation in neutralization of Ne+ on LiF(001)

Neutralization of low keV Ne+ ions at a LiF(001) surface is studied in a grazing incidence geometry. The combination of energy loss and electron spectroscopy in coincidence reveals two neutralization channels of comparable importance. Besides the Auger process, the Ne+ neutralization can proceed via peculiar target excitation, corresponding to the formation of an electron bihole complex termed trion.