MPI Campus Seminar: Following the energy transfer between hydrogen atoms and surfaces using scattering experiments

MPI Campus Seminar

  • Date: Jun 23, 2021
  • Time: 11:00 - 12:00
  • Speaker: Kerstin Krüger
  • Department of Dynamics at Surfaces
  • Location: Max-Planck-Institut für biophysikalische Chemie (MPIBPC)
  • Room: Online
  • Host: S. Glöggler, A. Godec, A. Faesen, J. Liepe, S. Meek, A. Stein, M. Wilczek, S. Karpitschka, D. Zwicker, M. Oudelaar, L. Andreas
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MPI Campus Seminar: Following the energy transfer between hydrogen atoms and surfaces using scattering experiments
Hydrogen atom scattering from various surfaces under ultra-high vacuum conditions is used
to investigate the process of energy transfer during the interaction of impinging atoms with
a surface sample, thereby providing information about surface dynamics and important
steps in surface reactions, e.g. chemical binding and adsorption. The simplicity of the system
makes it particularly interesting for a detailed comparison between high-level experiments
and first principle theories.

Photolysis of hydrogen halide molecules with ultraviolet or vacuum-ultraviolet photons
generates nearly monoenergetic atomic hydrogen beams with translational energies in the
range of 0.4 to 7 eV. These hydrogen atoms are scattered from the surface sample, and their
translational energy after the collision is probed by the Rydberg-atom time-of-flight method
to obtain scattering-angle resolved translational energy loss spectra.
For an insulating surface, it was shown that the collisions are nearly elastic, whereas
hydrogen atoms colliding with a metal surface possess a large translational energy loss that
can be explained by energy transfer to electron-hole pair excitation.
[1] In contrast, for hydrogen atoms colliding with epitaxial graphene grown on a platinum (111) substrate, the
formation of a transient chemical bond could be observed. Here, the scattering distributions
exhibit a bimodal behaviour with a strongly inelastic and a nearly-elastic scattering channel,
depending on whether the barrier to chemical bond formation is overcome or not,

In a current project we investigate hydrogen atom scattering from a semiconducting,
reconstructed germanium (111) surface. Again, two different scattering channels are
observed, potentially arising from nearly-elastic energy transfer and either electronic
excitation over the surface band gap or the formation of a transient bond. To further
elucidate the experimental findings, comparison with theoretical models will be required.
Because of the surface reconstruction, this system represents a particularly challenging, yet
very interesting task for theoretical simulations.

[1] O. Bünermann et al., Science 2015, 350, 1346.
[2] H. Jiang et al., Science 2019, 364, 379
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