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# A momentum space view of the surface chemical bond

Karl-Franzens University, Universitätsplatz 5, 8010 Graz, Austria.

Physical Chemistry Chemical Physics (Impact Factor: 4.2). 03/2011; 13(9):3604-11. DOI: 10.1039/c0cp01458c Source: PubMed

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Peter Puschnig, Jun 23, 2015 Available from: Data provided are for informational purposes only. Although carefully collected, accuracy cannot be guaranteed. The impact factor represents a rough estimation of the journal's impact factor and does not reflect the actual current impact factor. Publisher conditions are provided by RoMEO. Differing provisions from the publisher's actual policy or licence agreement may be applicable.

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**ABSTRACT:**Graphene's peculiar electronic band structure makes it of interest for new electronic and spintronic approaches. However, potential applications suffer from quantization effects when the spatial extension reaches the nanoscale. We show by photoelectron spectroscopy on nanoscaled model systems (disc-shaped, planar polyacenes) that the two-dimensional band structure is transformed into discrete states which follow the momentum dependence of the graphene Bloch states. Based on a simple model of quantum wells, we show how the band structure of graphene emerges from localized states, and we compare this result with ab initio calculations which describe the orbital structure.New Journal of Physics 11/2012; 14:113008. DOI:10.1088/1367-2630/14/11/113008 · 3.67 Impact Factor - [Show abstract] [Hide abstract]

**ABSTRACT:**We present a computational study on the angular-resolved photoemission spectra (ARPES) from a number of polycyclic aromatic hydrocarbons and graphene. Our theoretical approach is based on ab-initio density functional theory and the one-step model where we greatly simplify the evaluation of the matrix element by assuming a plane wave for the final state. Before comparing our ARPES simulations with available experimental data, we discuss how typical approximations for the exchange-correlation energy affect orbital energies. In particular, we show that by employing a hybrid functional, considerable improvement can be obtained over semi-local functionals in terms of band widths and relative energies of π and σ states. Our ARPES simulations for graphene show that the plane wave final state approximation provides indeed an excellent description when compared to experimental band maps and constant binding energy maps. Furthermore, our ARPES simulations for a number of polycyclic aromatic molecules from the oligo-acene, oligo-phenylene, phen-anthrene families as well as for disc-shaped molecules nicely illustrate the evolution of the electronic structure from molecules with increasing size towards graphene.Journal of Electron Spectroscopy and Related Phenomena 06/2015; 200. DOI:10.1016/j.elspec.2015.06.003 · 1.55 Impact Factor -
##### Article: Complete determination of molecular orbitals by measurement of phase symmetry and electron density.

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**ABSTRACT:**Several experimental methods allow measuring the spatial probability density of electrons in atoms, molecules and solids, that is, the absolute square of the respective single-particle wave function. But it is an intrinsic problem of the measurement process that the information about the phase is generally lost during the experiment. The symmetry of this phase, however, is a crucial parameter for the knowledge of the full orbital information in real space. Here, we report on a key experiment that demonstrates that the phase symmetry can be derived from a strictly experimental approach from the circular dichroism in the angular distribution of photoelectrons. In combination with the electron density derived from the same experiment, the full quantum mechanical wave function can thus be determined experimentally.Nature Communications 06/2014; 5:4156. DOI:10.1038/ncomms5156 · 10.74 Impact Factor