Inverse photoemission spectroscopy of H, CO and NO adsorbed at Ni(100) and Ni(111) surfaces

Reimer, W.; Fink, Th.; Küppers, J.

doi:10.1016/0039-6028(88)90335-4

Cited by 50 publications

(12 citation statements)

References 37 publications

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“…1.5 eV, and therefore consistent with inverse photoemission data, which place the center of the 2* resonance of adsorbed NO 1.5 eV above the Fermi level. 37 The absorbed energy is not entirely dissipated-rather, an energy gain of ⌬͗E͘ϭ͗E͘(T)Ϫ⑀ 0g ϭ0.022 eV is observed.…”

Section: A Estimating a Resonance Lifetimementioning

confidence: 97%

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Quantum dynamics of bond breaking in a dissipative environment: Indirect and direct photodesorption of neutrals from metals

Saalfrank

Kosloff

1996

The Journal of Chemical Physics

119

115

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The dynamics of uv/visible laser-induced nonthermal desorption of neutral molecules from metal surfaces are studied by Liouville-von Neumann equations for quantum open systems. A one-dimensional, two-state Gadzuk-Antoniewicz model is adopted, representative for NO/Pt͑111͒. Electronic quenching due to coupling of the adsorbate negative ion resonance to the metal electrons is treated within the Lindblad dynamical semigroup approach. Both indirect ͑hot-electron mediated͒ and hypothetical direct ͑dipole͒ excitation processes are considered. For the indirect pathways, DIET ͑single-excitation͒ and DIMET ͑multiple-excitation͒ limits are studied using one-and double-dissipative channel models, respectively. To reproduce experimental desorption yields and desorbate translational energies, we estimate the quenching lifetime for NO/Pt͑111͒ to be less than 5 fs. We also extend previous quantum treatments of photodesorption processes to the case of coordinate-dependent quenching rates. Further, the characteristic scaling laws of desorption yields versus laser fluence are derived for each of the individual excitation pathways. Finally, the possibility to control photoreactivity at surfaces by different, vibration-promoted schemes ͑surface heating, irϩuv two-photon strategies, use of pulsed uv lasers͒ is examined.

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Section: A Estimating a Resonance Lifetimementioning

confidence: 97%

“…With the new potential parameters, the vertical excitation energy ͉g͘→͉e͘ becomes Ϸ1.5 eV ͑previously Ϸ2.5 eV͒, and fits now the experimental estimate. 37 The two-state system Hamiltonian is written as Ĥ ϭĤ e ͉e͗͘e͉ϩĤ g ͉g͗͘g͉ϩV eg ͉e͗͘g͉ϩV ge ͉g͗͘e͉, ͑2.3͒…”

Section: A Potentials and Hamiltonianmentioning

confidence: 99%

Quantum dynamics of bond breaking in a dissipative environment: Indirect and direct photodesorption of neutrals from metals

Saalfrank

Kosloff

1996

The Journal of Chemical Physics

119

115

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“…In the adsorbed state one expects therefore the 2re manifold to straddle the Fermi level. IPE spectra of adsorbed NO have been reported by Rogozik et al [34] for Pd(100), by Johnson and Hulbert [14] for Ni(100) and Pd(111), and by Reimer et al [35] for Ni(100) and Ni(111). In all these cases the 2n* derived IPE structure appears 1.5-1.8 eV above E F with its tail Nevertheless the interpretation of the IPE spectra -as well as the UPS spectra -of adsorbed NO remains controversial [2,14,36].…”

Section: Strong Chemisorption: Diatomic Moleculesmentioning

confidence: 85%

Unoccupied electronic states in adsorbate systems

Bertel

1991

Appl. Phys. A

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Abstract. Experimental work on unoccupied electronic states in adsorbate systems on metallic substrates is reviewed with emphasis on recent developments. The first part is devoted to molecular adsorbates. Weakly chemisorbed hydrocarbons are briefly discussed. An exhaustive inverse photoemission (IPE) study of the CO bond to the transition metals Ni, Pd, and Pt is presented. Adsorbed NO is taken as an example to demonstrate the persisting discrepancies in the interpretation of IPE spectra. Atomic adsorbates are discussed in the second part. The quantum well state model is applied to interpret the surface states in reconstructing and non-reconstructing adsorption systems of alkali metals and hydrogen. A recent controversy on the unoccupied electronic states of the Cu(110)/O p(2 × i) surface is critically reviewed. The quantum well state model is then compared to tight binding and local-density-functional calculations of the unoccupied bands and the deficiencies of the various approaches are pointed out. Finally, the relation between the surface state model and more chemically oriented models of surface bonding is briefly discussed.PACS: 73.20.Hb, 79.60.-i A knowledge of unoccupied electronic states in adsorbate systems is crucial to the understanding of the surface chemical bond. The unoccupied levels determine the reactivity of surfaces and surface species just as much as the occupied levels do. One example out of many is provided by the hydrogen dissociation on Ni, where the empty Ni d-levels as hole reservoirs and are indispensable for the reaction to proceed [-1]. Another motivation for the study of unoccupied states derives from the fact that widely used techniques, such as scanning tunneling microscopy (STM) or second harmonic generation (SHG) on surfaces are based on processes involving empty levels. A thorough understanding of these processes therefore requires a knowledge of the unoccupied electronic level structure. There are, however, only a limited number of techniques available for providing independent information on the empty states. Ultraviolet photoelectron spectroscopy (UPS), where the unoccupied levels are probed as final states in k-conserving dipole transitions, and secondary electron spectroscopy, which may also yield information on the kll resolved unoccupied density of states, only access empty states above the vacuum level. This is a serious restriction if one considers the fact that the chemical bond involves primarily the "frontier orbitals", i.e. the highest occupied and the lowest unoccupied adsorbate orbitals and substrate Bloch states, which in an adsorbate system are usually aUtogether located below the vacuum level. Similarly, the position of the empty states involved in STM and SHG is in general restricted to a narrow range extending a few eV above the Fermi level. Spectroscopy of the near-edge X-ray absorption fine structure (NEXAFS) is a valuable tool for probing final states just above the Fermi level, but the presence of a core hole in the final state commonly results in large ...

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“…The 2π* level of free NO is singly occupied, and is broadened as the molecule interacts with the surface sp‐band continuum . This is in contrast to the case of NO on transition metal surfaces, where the 2π* orbital is heavily hybridized with the d‐band and new states appear at ≈2 eV below and above the Fermi level . These situations are qualitatively related to the two simple limits of the Newns–Anderson model for chemisorption …”

Section: The No–substrate Interactionmentioning

confidence: 94%

“…On transition metal surfaces, the 2π* orbital is hybridized with narrow d‐bands through donation and backdonation processes, resulting in the loss of the unpaired electron . The 2π*‐derived states appear below (bonding) and above (antibonding) the Fermi level, and were observed by (inverse) photoemission experiments …”

Section: Introductionmentioning

confidence: 99%

Imaging Molecular Interaction of NO on Cu(110) with a Scanning Tunneling Microscope

Okuyama

2014

The Chemical Record

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Molecular interaction on metal surfaces is one of the central issues of surface science for the microscopic understanding of heterogeneous catalysis. In this Personal Account, I review the recent studies on NO/Cu(110) employing a scanning tunneling microscope (STM) to probe and control the molecule-molecule interaction on the surface. An individual NO molecule was observed as a characteristic dumbbell-shaped protrusion, visualizing the 2π* orbital. By manipulating the intermolecular distance with the STM, the overlap of the 2π* orbital between two NO molecules was controlled. The interaction causes the formation of the bonding and antibonding orbitals below and above the Fermi level, respectively, as a function of the intermolecular distance. The 2π* orbital also plays a role in the reaction of NO with water molecules. A water molecule donates a H-bond to NO, giving rise to the down-shift of the 2π* level below the Fermi level. This causes electron transfer from the substrate to NO, weakening, and eventually rupturing, the N-O bond. The facile bond cleavage by water molecules has implications for the catalytic reduction of NO under ambient conditions.

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Inverse photoemission spectroscopy of H, CO and NO adsorbed at Ni(100) and Ni(111) surfaces

Cited by 50 publications

References 37 publications

Quantum dynamics of bond breaking in a dissipative environment: Indirect and direct photodesorption of neutrals from metals

Quantum dynamics of bond breaking in a dissipative environment: Indirect and direct photodesorption of neutrals from metals

Unoccupied electronic states in adsorbate systems

Imaging Molecular Interaction of NO on Cu(110) with a Scanning Tunneling Microscope

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