Fine structure of the two-photon photoemission from benzene adsorbed on Cu(111)

Munakata, Toshiaki; Sakashita, Tatsuo; Tsukakoshi, Motowo; Nakamura, Junko

doi:10.1016/s0009-2614(97)00458-2

Cited by 34 publications

(19 citation statements)

References 14 publications

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“…The hollow adsorption site and the planar configuration of the molecule ͑with the canting of the H atoms͒ is generally found in experimental studies of benzene adsorption on metal surfaces. [9][10][11][12][13][14] This geometric configuration is characteristic of bonding via the -* complex of molecular orbitals.…”

Section: Discussionmentioning

confidence: 99%

“…Theoretical studies of benzene on copper ͑110͒ and ͑111͒ surfaces [6][7][8] have been complementing experimental studies of these two surfaces. [9][10][11][12][13][14] Less work has been done on the ͑100͒ surface. 7 On the ͑111͒ and ͑100͒ surfaces it is generally concluded that benzene adsorbs with the aromatic ring parallel to the surface.…”

Section: Introductionmentioning

confidence: 99%

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Chemisorption of benzene and STM dehydrogenation products on Cu(100)

et al. 2003

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Modification of individual chemisorbed benzene molecules on Cu͑100͒ has recently been performed in atomic manipulation experiments ͓J. Phys. Chem. A. 104, 2463 ͑2000͒; Surf. Sci 451, 219 ͑2000͔͒. Benzene dissociates under controlled voltage pulses in a scanning tunneling microscope ͑STM͒ junction. The reaction is characterized as a dehydrogenation process and the fragments are identified as benzyne, C 6 H 4 . Here we present a density functional theory investigation of the chemisorption of benzene on the Cu͑100͒ surface, the nature of the bonding and its effect on the STM images. The fragments phenyl and benzyne formed after one-fold and two-fold dehydrogenation of chemisorbed benzene are studied in the same manner. The stability of the fragments is explored via their chemisorption energy, their electronic structure on the surface and their affinity for hydrogen. Benzyne fragments seem to be the most stable, in agreement with the conclusion of the aforementioned STM experiments.

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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Chemisorption of benzene and STM dehydrogenation products on Cu(100)

et al. 2003

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“…Vibrational structure in 2PPE spectroscopy for adsorbed molecules will provide rich information on carrier dynamics at surfaces and interfaces, though vibrational resolution in 2PPE for adsorbed molecules was not very clear so far. 7 Here, we report vibrationally resolved features in 2PPE spectra for lead phthalocyanine ͑PbPc͒ films formed on highly oriented pyrolytic graphite ͑HOPG͒.…”

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confidence: 91%

Vibrationally resolved two-photon photoemission spectroscopy for lead phthalocyanine film on graphite

et al. 2009

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Vibronic structure has been resolved in two-photon photoemission ͑2PPE͒ from the highest occupied molecular orbital ͑HOMO͒-derived level of lead phthalocyanine film formed on graphite. The 2PPE from the HOMO-derived level was enhanced by the resonance with the third lowest unoccupied molecular orbital ͑LUMO+ 2͒-derived level. At photon energies below and well above the resonance, the intensity of the vibronic structure was similar to that of one-photon photoemission. On the other hand, the vibronic structure was significantly weak at photon energies slightly above ͑Ͻ0.4 eV͒ the resonance. The decrease in the vibronic structure was attributed to the nuclear motion of molecule in the intermediate state associated with LUMO +2.The interaction of electron and hole with phonon is a key for electric conduction in solids as well as at interfaces. As for carrier transportation in organic semiconductors, the role of vibronic coupling has been discussed. 1,2 The holevibrational coupling at interfaces between organic molecular films and substrates has recently been resolved in photoemission spectroscopy and was discussed in relation to the holehopping mobility and the reorganization energy. 3,4 Experimental detection of the nuclear motion of molecule triggered by injection of electron into an unoccupied state is the next step to be explored for deeper understanding of electron transportation at the interface between inorganic substrate and organic film. Nuclear wave-packet motion of adsorbed atoms in an unoccupied state was reported as the real-time observation of a surface photochemical reaction. 5 On the other hand, vibration of molecule in an electronic excited state can be resolved only for thick films and is hardly resolved for the first adsorbed layer because lifetime of the excited state becomes too short by interaction with the substrate. 6 Two-photon photoemission ͑2PPE͒ spectroscopy gives spectroscopic and dynamic information on both occupied and unoccupied energy levels. Vibrational structure in 2PPE spectroscopy for adsorbed molecules will provide rich information on carrier dynamics at surfaces and interfaces, though vibrational resolution in 2PPE for adsorbed molecules was not very clear so far. 7 Here, we report vibrationally resolved features in 2PPE spectra for lead phthalocyanine ͑PbPc͒ films formed on highly oriented pyrolytic graphite ͑HOPG͒.In our former 2PPE work for PbPc/HOPG, we have identified molecule-derived levels due to the next highest occupied molecular orbital ͑HOMO-1͒, HOMO, the lowest unoccupied molecular orbital ͑LUMO͒, LUMO+ 1, LUMO+ 2 as well as the first image potential state ͑IPS͒. Resonant excitation from the HOMO level to the LUMO+ 2 level was observed. 8 In this Brief Report, we examined the detailed spectral profiles of the HOMO-and LUMO+ 2-derived peaks at photon energies below and above the resonance. The vibrational satellite of the HOMO peak was found to be dependent on the excitation photon energy. The dependence was attributed to the nuclear motion of the molecule in the LUMO...

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“…2 2PPE was used in various adsorbate-surface systems to study adsorbateinduced and image potential states. [2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17] The variety of adsorbates investigated on the Cu͕111͖ surface spans from small molecules, like CO, 7 through atomic overlayers, like Xe, 9 to larger molecules, like C 6 H 6 . 14,15 In this paper we present a 2PPE investigation of the C 6 H 6 bilayer coverage on Cu͕111͖.…”

Section: Introductionmentioning

confidence: 99%

Electronic states of the C6H6/Cu{111} system: Energetics, femtosecond dynamics, and adsorption morphology

Velič

Hotzel

Wolf

et al. 1998

The Journal of Chemical Physics

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Two-photon-photoemission ͑2PPE͒ spectroscopy is employed to characterize electronic states of a bilayer C 6 H 6 /Cu͕111͖ system at 85 K. The unoccupied benzene * e 2u state is observed with a binding energy of 4.6 eV above the Fermi level. This result agrees with inverse-photoemission ͑IPE͒ data and provides a case where the determination of the binding energy is identical for 2PPE and IPE. The * e 2u state is assigned in the 2PPE scheme as a final state which is the first observed final state in 2PPE of adsorbate-surface systems. The dependence of the electron dynamics on the morphology of an incomplete adsorption layer is also investigated. Two (nϭ1)-like image potential states A and B are observed which presumably originate from two different C 6 H 6 adsorption geometries in the bilayer regime. The two image states A and B are characterized by electron effective masses of 1.1 and 1.9 m e , binding energies of 3.30 and 3.45 eV above the Fermi level, and lifetimes of 40 and 20 fs, respectively. The dielectric continuum model and the Kronig-Penney model are employed to simulate the origin of (nϭ1)-like image states. The work function decreases from 4.9 eV at clean Cu͕111͖ to 4.0 eV at bilayer coverage. The change of the work function and the observation of two image states suggest the redefining of the ratio of the numbers of benzene molecules in the first and the second layers of the bilayer regime to approximately 1:1 instead of 1:2, as previously reported. 2PPE is shown to be sensitive to the changes of morphologies, local work functions, and adsorbate-surface potentials during the layer formation.

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Fine structure of the two-photon photoemission from benzene adsorbed on Cu(111)

Cited by 34 publications

References 14 publications

Chemisorption of benzene and STM dehydrogenation products on Cu(100)

Chemisorption of benzene and STM dehydrogenation products on Cu(100)

Vibrationally resolved two-photon photoemission spectroscopy for lead phthalocyanine film on graphite

Electronic states of the C6H6/Cu{111} system: Energetics, femtosecond dynamics, and adsorption morphology

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