Hans Kirchner
Physikalisch-technische Bundesanstalt, National Metrology Institute, Braunschweig, GERMANY
Photoemission Orbital Tomography (POT) is an experimental/theoretical approach that utilizes angle-resolved photoemission spectroscopy to obtain electron distribution maps of molecular orbitals in momentum space (k-maps) at constant binding energy. A real-space image reconstruction of these k-maps by a Fourier transformation is possible with the plane wave approximation (PWA) for the final state, which assumes a freely outgoing electron.
POT has been successfully applied to organic molecules and two-dimensional materials, offering applications such as spectral deconvolution, geometric information extraction, and reaction product identification. However, the well-established PWA can be problematic in certain scenarios, including photon energy dependence, circular dichroism, and specific experimental geometries.
Recent developments have addressed these challenges by transitioning from the PWA to an interfering combination of outgoing spherical waves. Experimental confirmation of these energy-dependent studies required a light source with a well-defined energy resolution and photon flux, provided by the national metrology institute of Germany, the Physikalisch-Technische Bundesanstalt (PTB).
In addition, time-resolved POT has been explored to visualize electron dynamics in molecular orbitals by combining POT, ultrafast photoelectron spectroscopy, and advanced theory.
This talk will summarize these recent advancements in POT, highlighting the potential and limitations of this powerful technique for studying molecular orbitals.