Capture of polarized electrons into excited terms of fast atoms during grazing surface collisions

Abstract

Atoms, Molecules zo,,oo.r,, and ClustersAbstract. Fast ions are scattered from magnetized surfaces under grazing angles of incidence. During the interaction with the surface charge exchange is effective and results in a population of stable and excited atomic terms. This capture of electrons is characterized by anisotropic distributions of atomic orbital angular momenta and in addition -for magnetized targets -by anisotropic distributions of electronic spins. We will discuss in some detail, how these anisotropic distributions can be studied via the analysis of the state of polarization of the fluorescent light, emitted in electronic transitions from excited terms of free atoms after the impact with the surface. We show that a defined variation of the magnetization of the target affects the polarization of the emitted light in a characteristic way, which allows to deduce the electronic spin polarization of the atoms. The method implies some perspectives with respect to the study of magnetic properties of the vacuum-solid interface well above the topmost layer of surface atoms. 34.50.Fa of this paper is to outline in some detail the concepts and experimental procedures of our studies. PACS:We will discuss first the capture of polarized electrons into atomic terms during ion-surface collisions and its effect on the anisotropic distribution of angular momenta in free atoms. This anisotropy is investigated by the analysis of the (polarized) light emitted in transitions from excited atomic terms after the interaction with the surface. Based on a theoretical description of the coupling of anisotropic ensembles of angular momenta and spins, we obtain the atomic and electronic spin polarization from an analysis of the light polarization for defined settings of the magnetization of the target. Then we describe the application of this procedure to the capture of polarized electrons into a number of different excited terms of atoms/ions with different orbital angular momenta and multiplicities. After a presentation and discussion of our experimental results we will outline concepts of charge exchange in grazing surface collisions and its relevance and perspectives with respect to the capture of polarized electrons.

Magnetic interface coupling between ultrathin Co andNixMn100−xfilms on Cu(001)

“…Such a method is the detection of polarized fluorescence light emitted from He atoms which are excited by EC during grazing scattering from a surface. 13,[38][39][40][42][43][44][45] Under defined conditions, EC hysteresis loops are obtained by monitoring the Stokes parameter S / I as a function of the external magnetic field. The reversible part of the surface magnetization is related to the normalized parameter ⌬S / I = S / I͑ ↑ ͒ − S / I͑ ↓ ͒ with the Stokes parameter S / I͑ ↑ ͒ and S / I͑ ↓ ͒ for reversed settings of the magnetization.…”

Thin Co films on Cu(111) studied by electron capture spectroscopy

“…3 The sense of rotation and degree of polarization are directly related to the spin polarization P s . 4 By measuring the difference signal for opposite magnetization S/I " S/I # D S/I , Ł Correspondence to: Marika Schleberger, Universität Duisburg-Essen, Institut für Experimentelle Physik, 45117 Essen, Germany. E-mail: marika.schleberger@uni-essen.de † (In the early experiments of Rau and Sizman the spin polarization was deduced from a subsequent nuclear reaction.).…”

Na*(3p)-Formation under grazing scattering of Na+-ions at an Al(111) surface

“…Polarization measurements have not been published for this system as yet, but for Cu(111) at intermediate impact energies (100-300 keV) [14], for Ni(lll) at low energies (3-29 keV) [15] and for Fe(ll0) at 3 to 350 keV [16]. The quantitative understanding of Na* (3p)-formation near AI(111) may also be considered as a prerequisite for any understanding of the chargetransfer dynamics in Na*(3p)-population in front of magnetized surfaces, which may serve as a probe to investigate surface magnetism [16][17][18]. Level widths and shifts are already available for the lowest excited states of alkali atoms near jellium surfaces [8]+ Here we will report on calculations ofNa* (3p)-formation under grazing angle collisions with an Al-like jellium surface in dependence on the projectile velocity.…”