• DOI:10.1126/science.1176105
• Corpus ID: 5476218

Reconstruction of Molecular Orbital Densities from Photoemission Data

@article{Puschnig2009ReconstructionOM,
  title={Reconstruction of Molecular Orbital Densities from Photoemission Data},
  author={Peter Puschnig and Stephen P. Berkebile and Alexander J. Fleming and Georg Koller and Konstantin V. Emtsev and Thomas Seyller and J. D. Riley and Claudia Ambrosch-Draxl and Falko P. Netzer and Michael G. Ramsey},
  journal={Science},
  year={2009},
  volume={326},
  pages={702 - 706}
}

• P. Puschnig, S. Berkebile, +7 authors M. Ramsey
• Published 30 October 2009
• Physics, Chemistry
• Science

Electron Comings and Goings Advances in computational chemistry have enabled remarkably detailed calculations of electrons' spatial arrangements in complex molecules. Experimental confirmation of these orbital geometries remains challenging, however, particularly for molecules bound in thin layers to underlying surfaces—a morphology of increasing interest in organic semiconductor development. Puschnig et al. (p. 702, published online 10 September) mapped the trajectories of photoelectrons emitted from polycyclic aromatic molecules deposited on copper and extracted spatial profiles of the orbitals from which these electrons emerged. The method of analysis takes advantage of the straightforward Fourier relation between position and momentum and complements orbital imaging techniques based on scanning tunneling microscopy. Maps of photoelectron momentum can reveal the orbital geometries of aromatic molecules adsorbed on surfaces. Photoemission spectroscopy is commonly applied to study the band structure of solids by measuring the kinetic energy versus angular distribution of the photoemitted electrons. Here, we apply this experimental technique to characterize discrete orbitals of large π-conjugated molecules. By measuring the photoemission intensity from a constant initial-state energy over a hemispherical region, we generate reciprocal space maps of the emitting orbital density. We demonstrate that the real-space electron distribution of molecular orbitals in both a crystalline pentacene film and a chemisorbed p-sexiphenyl monolayer can be obtained from a simple Fourier transform of the measurement data. The results are in good agreement with density functional calculations.