Energy Transfer from Fast Atomic Projectiles to a Crystal Lattice under Channeling Conditions

Mertens, A.; Winter, H.

doi:10.1103/physrevlett.85.2825

Cited by 50 publications

(26 citation statements)

References 23 publications

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“…The energy of the projectiles in the keV regime results in an efficient detection of scattered atoms and angular distributions can be recorded within less than a minute with some 10 5 particles impinging on a macroscopic surface area. Therefore, modifications of the surface can be neglected [13,14]. Among these techniques, especially fast atom diffraction (FAD) [11,[15][16][17][18][19][20][21][22] with de Broglie wavelengths of some 0.001Å gained considerable interest and motivated numerous studies with respect to FADs phenomenological description [23][24][25][26][27][28][29][30][31][32][33][34][35][36] and utilization for epitaxial growth monitoring [37,38] as well as qualitative and quantitative structure determination [19][20][21]33,[39][40][41][42][43][44][45].…”

Section: Introductionmentioning

confidence: 99%

Quantitative structure determination using grazing scattering of fast atoms: Oxygen-induced missing-row reconstruction of Mo(112)

Seifert

Winter

2016

Phys. Rev. B

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We present an extensive study on the structure of oxygen adsorbates on Mo(112) by means of grazing scattering of fast hydrogen and helium atoms and low-energy electron diffraction. For projectile energies less than 2 keV, fast atom diffraction provides information on the surface unit cell and on adsorption sites for low coverages. In the classical scattering regime, we employed so-called triangulation techniques where for an azimuthal rotation of the target axial surface channels are identified. From comparison with computer simulation positions of surface atoms can be derived. Aside from the detection scheme of projectile-induced electron emission, we present details for a new variant of triangulation based on the detection of angular distributions of scattered particles. The different sensitivity of the methods to the topmost surface layers allows us to efficiently set up structural models for four adsorbate phases for which contradicting models exist in literature. The c(4×2) phase is revealed to be one step in the formation of a missing-row reconstruction with p(1×2) unit cell. Our studies demonstrate the potential of grazing scattering of fast atoms for quantitative structure analysis.

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Section: Introductionmentioning

confidence: 99%

Quantitative structure determination using grazing scattering of fast atoms: Oxygen-induced missing-row reconstruction of Mo(112)

Seifert

Winter

2016

Phys. Rev. B

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“…Electronically inelastic processes lead to ''strong'' decoherence or dissipation [13]. Weak decoherence originates from momentum transfers in binary He-F and He-Li collisions, which result in phonon excitations [15]. Their longitudinal, Pðq k Þ, and transverse, Pðq ?…”

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Suppression of Decoherence in Fast-Atom Diffraction at Surfaces

et al. 2008

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Scattering of fast neutral atoms with keV kinetic energies at alkali-halide surfaces under grazing angles displays intriguing diffraction patterns. The surprisingly strong persistence of quantum coherence despite the impulsive interaction with an environment at solid state density and elevated temperatures raises fundamental questions such as to the suppression of decoherence and of the quantum-to-classical crossover. We present an ab initio simulation of the quantum diffraction of fast helium beams at a LiF (100) surface in the h110i direction and compare with recent experimental diffraction data. From the quantitative reconstruction of diffraction images the vertical LiF-surface reconstruction, or buckling, can be determined. DOI: 10.1103/PhysRevLett.101.253201 PACS numbers: 34.35.+a, 61.85.+p, 68.49.Bc, 79.20.Rf Diffraction of massive particles scattered at surfaces was one of the key experiments establishing the quantum wave nature. Coherent atom and molecule optics was initiated when Estermann and Stern [1] observed interference patterns of slow (''thermal'') helium atoms and H 2 molecules scattered off alkali-halide surfaces. Thermal atom scattering (TAS) [2,3] as well as low-energy electron diffraction (LEED) [4] are nowadays routinely employed to accurately probe properties of surfaces. These techniques exploit the fact that the de Broglie wavelength dB of the beam particles is comparable to the lattice constant a. More recently, probing the wave nature of massive objects has taken center stage in exploring the quantum-toclassical crossover [5,6]. One ingredient of the quantumto-classical transition is the limit of small de Broglie wave length dB ! 0, the other the ubiquitous presence of unobserved environmental degrees of freedom within the framework of decoherence theory [1], or alternatively, elements beyond standard unitary quantum dynamics, including the frequently involved ''collapse'' of the wave functions [7,8]. In matter-wave interferometry of large and complex biomolecules, de Broglie wavelengths as small as few picometer (10 À12 m) have been reached [6].Even shorter wavelengths have been accessed by recent fast-atom scattering studies at surfaces [9-11] with dB as small as % 200 femtometers. Persistence of quantum diffraction and the apparent suppression of decoherence is all the more remarkable, as thermal fluctuation amplitudes of the surface atoms are much larger than dB and, moreover, collisions with keV projectile energies would strongly suggest the dominance of dissipative and decohering processes. In this Letter we present an ab initio simulation of fast helium atom diffraction ( 4 He) at a LiF (100) surface. We analyze the suppression of decoherence in grazingincidence scattering within an open quantum system (OQS) approach and quantitatively reconstruct experimental diffraction images [9,10] in considerable detail. Fastatom diffraction has the potential to become a powerful tool to interrogate structural and dynamical properties of surfaces.Fast-atom scattering at surfaces under s...

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“…11 The energy-loss contribution originating from elastic collisions is negligible, especially in view of multiple scattering. 12 Contributions originating from processes outside the defined interaction zone are small and can be estimated to be of the order of a few electron-volts. 8 The trajectory calculations result in critical angles for axial channeling of the order of 2-3°for the presented keV regime.…”

Section: Conceptmentioning

confidence: 99%

Electronic stopping of keV nitrogen ions interacting with a Pt(110)(1 × 2) surface—a tool to characterize electronic surfaces

Robin

Postnikov

Heiland

2005

Surface & Interface Analysis

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Ion channeling is used to investigate the electronic density corrugation at surfaces by analysing the electronic stopping behaviour of ions scattering grazingly off a clean single crystalline Pt(110).1 × 2/ surface. We use the fact that under these conditions the elastic contribution can be separated from the inelastic energy-loss processes, which are closely related to the electronic density sampled along the projectiles trajectories. Therefore, we have a direct probe of the surface electronic density structure. Here, experiments and their theoretical interpretation for N + ions at primary ion energies of 1-10 keV are presented. Multi-peak features of the energy spectra, depending on the azimuthal surface orientation, are attributed to different particle trajectories. A detailed analysis of trajectory calculations affords an unambiguous assignment of the observed peak structures to three trajectory classes, each sampling specific energy losses. The comparison of the experimental energy-loss values with results obtained from a surfaceadapted energy-loss model for ion scattering that includes the electron density allows us to investigate the electronic surface of the sample. The results are compared with calculated surface electron density contours. Reasonable agreement is obtained, showing that the presented method is suitable to characterize the electronic density structure at crystalline surfaces.

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Energy Transfer from Fast Atomic Projectiles to a Crystal Lattice under Channeling Conditions

Cited by 50 publications

References 23 publications

Quantitative structure determination using grazing scattering of fast atoms: Oxygen-induced missing-row reconstruction of Mo(112)

Quantitative structure determination using grazing scattering of fast atoms: Oxygen-induced missing-row reconstruction of Mo(112)

Suppression of Decoherence in Fast-Atom Diffraction at Surfaces

Electronic stopping of keV nitrogen ions interacting with a Pt(110)(1 × 2) surface—a tool to characterize electronic surfaces

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