He-diffraction studies of hydrogen chemisorption on rhodium (311)

Apel, R.; Farı́as, Daniel; Tröger, H.; Rieder, Karl–Heinz

doi:10.1016/0039-6028(95)00154-9

Cited by 12 publications

(8 citation statements)

References 9 publications

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“…This situation was clarified in a series of HAS studies performed by Apel et al (1995aApel et al ( , b, 1996, who observed the formation of a well-ordered (1 × 1)H phase before completion of the (1 × 3)H phase. Figure 8 shows the development of in-plane spectra from Rh(311) with increasing hydrogen exposure at 110 K. The appearance of a (1 × 1)H structure, which requires a coverage of 1 ML, after exposure to ∼0.2 L demonstrates that the initial sticking Lehmann et al (1996) bromohexane KBr 100(1 × 2) 1 140 Hernández et al (1996) water MgO(100) c(4 × 2) ?…”

Section: Adsorption On Metal Surfacesmentioning

confidence: 97%

“…We will begin our discussion with the HAS investigations of the H/Rh(311) adsorption system reported by Apel et al (1995aApel et al ( , b, 1996. This system had been previously investigated by LEED, TDS and work function measurements by Nichtl-Pecher et al (1991), who found a succession of (1 × 3)H, (1 × 2)H, (1 × 3)2H and (1 × 2) REC superstructures with increasing hydrogen exposure.…”

Section: Adsorption On Metal Surfacesmentioning

confidence: 98%

“…A comparison of the profiles 311with increasing exposure at 110 K as observed with He diffraction. From Apel et al (1995a).…”

Section: Adsorption On Metal Surfacesmentioning

confidence: 99%

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Atomic beam diffraction from solid surfaces

1998

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Atomic beam techniques are presently being used in many branches of surface physics such as studies of the particle-surface physisorption potential, surface structure, surface phonons, nucleation and growth on metal and insulator surfaces, surface diffusion and accommodation and sticking of molecules. This review concentrates on diffractive phenomena from surfaces, which up to now were investigated mainly with helium. The theoretical background for diffraction calculations is outlined and representative examples of different applications are given. The main subjects covered are: structural determinations of chemisorbed and physisorbed systems, investigations of disordered surfaces, selective adsorption resonances, diffusion and nucleation studies and investigations of growth and phase transitions on surfaces. Diffraction results obtained with Ne, Ar, H 2 and D 2 are also summarized.

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Section: Adsorption On Metal Surfacesmentioning

confidence: 97%

Section: Adsorption On Metal Surfacesmentioning

confidence: 98%

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Atomic beam diffraction from solid surfaces

1998

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“…The polar and azimuthal orientation of the sample was determined to better than 0.2°through measurement of the diffraction peak positions on both the clean and the c(1ϫ1)H phase that, due to its larger corrugation, exhibits many more diffraction peaks. 19,20 This procedure was applied every time the sample was rotated 180°in the azimuthal direction to go from the ''upstairs'' to the ''downstairs'' scattering geometry and vice versa. All spectra shown here have been recorded in the sagittal plane ͑i.e., in the plane defined by the incident beam and the normal to the surface͒ with the incoming beam impinging perpendicular to the close-packed rows of the Rh͑311͒ surface.…”

Section: Experimental Descriptionmentioning

confidence: 99%

Scattering of He atoms from surface defects by grazing-angle diffraction beams

Farı́as¹,

Patting²,

Rieder³

et al. 2002

Phys. Rev. B

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It is experimentally demonstrated that diffraction beams from the scattering of He atoms from surfaces can be observed at grazing final angles of up to f Ϸ90°with respect to the surface normal. For He atom scattering from Rh͑311͒ under conditions in which a diffraction beam exits at a grazing angle, a broad scattered intensity appears that is interpreted as diffuse scattering from collisions with the small density of step defects resulting from the unavoidable miscut of the surface. Theoretical models for real and evanescent diffraction beams support the conclusion that this diffuse intensity is due to scattering by step defects from a diffraction beam under grazing exit conditions. For scattering in the plane perpendicular to the direction of the steps, this diffuse scattering signal is much stronger in one direction than in the opposite direction where the crystal azimuthal angle is rotated by 180°. The asymmetry in intensity is interpreted as due to the much larger number of steps up in one direction on the surface due to the crystal miscut, thus such measurements can uniquely determine the miscut direction. This experiment opens new possibilities for the characterization of surface defects with diffraction techniques.

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“…3,4 Both groups found a succession of superstructures: ͑1ϫ3͒H, ͑1ϫ2͒H, and ͑1ϫ2͒ REC with respect to the primitive unit cell ͑Table I͒. At an exposure intermediate between the exposures necessary for the two ͑1ϫ2͒ structures, the Erlangen group found an additional ͑1ϫ3͒2H superstructure which is rather tricky to prepare and was not pursued in our group.…”

Section: Introductionmentioning

confidence: 96%

Helium atom scattering and HREELS investigations of the H/Rh(311) adsorption system

Farı́as

Siebentritt

Apel

et al. 1997

The Journal of Chemical Physics

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Helium scattering structure analyses of the chemisorbed hydrogen phases on Co (1010) Hydrogen adsorption on Rh͑311͒ at 110 K leads to the appearance of ͑1ϫ1͒H, ͑1ϫ3͒H, ͑1ϫ2͒H and ͑1ϫ2͒ REC ordered layers. A previous He-atom scattering ͑HAS͒ investigation of the ͑1ϫ1͒H phase has revealed that its coverage is ⌰ϭ1 ML, whereby the H-atoms are adsorbed between the topmost bridge sites and the adjacent threefold hollow sites on the ͑111͒-microfacets. In this paper we present a combined HAS and HREELS structural analysis of the higher coverage phases. The structures derived from the HAS data show that, starting with the ͑1ϫ1͒H phase, the ͑1ϫ3͒H is formed by the adsorption of H-atoms in the wells between every third close-packed row, whereas adsorption on the same sites but between every second row leads to the completion of the ͑1ϫ2͒H phase. Accordingly, the corresponding coverages are 4/3 ML and 3/2 ML. The HREELS results clearly demonstrate the existence of two different H-species in the ͑1ϫ3͒H phase and three in the ͑1ϫ2͒H phase, supporting the HAS results.

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He-diffraction studies of hydrogen chemisorption on rhodium (311)

Cited by 12 publications

References 9 publications

Atomic beam diffraction from solid surfaces

Atomic beam diffraction from solid surfaces

Scattering of He atoms from surface defects by grazing-angle diffraction beams

Helium atom scattering and HREELS investigations of the H/Rh(311) adsorption system

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