Orbital Imaging for Chemical Analysis

About

I am YESP member Dr. Anja Meier (publication name: Haags) and currently work half-time as a postdoc and half-time as a scientific coordinator at the Institute for Quantum Nanoscience (PGI-3) under the direction of Prof. Dr. F. Stefan Tautz.

My research focuses on photoemission orbital tomography (POT), which is used to investigate the electronic and geometric properties of molecules and 2D materials. This involves combining experimental and theoretical data to gather information about the molecular orbitals of molecules on surfaces. Originally, it was thought that POT could only be used for certain systems, but the scope of POT is constantly expanding. The aim of my work is to identify the limits of the method.

In addition to static POT experiments of occupied states, it is also possible to image originally unoccupied molecular orbitals. For this purpose, POT is combined with ultrafast spectroscopy (pump-probe experiment). Here, the system under investigation is first brought into an excited electronic state with a first laser pulse, which is then measured with a second laser pulse delayed in time. We are investigating the dynamics of this process as part of the ERC Synergy Grant Orbital Cinema.

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Dr. Anja Meier

PGI-3

Building 02.4w / Room 326

+49 2461/61-85879

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Toroidal Electron Analyser

For photoemission tomography experiments we run a unique toroidal electron analyser, located permanently at the Metrological Light Source (MLS) of the Physikalisch-Technische Bundesanstalt (PTB) in Berlin.

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Electronic and Chemical Properties of Organic Molecules

Over the last years and in collaboration with our colleagues at Karl-Franzens Universtiy in Graz we have developed photoemission tomography into a powerful technique that provides direct access to the orbital structure of molecules (in particular of frontier orbitals that determine the electronic, optical and chemical properties of molecules) and thus helps revealing electronic and chemical states of molecules at surfaces.

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Tracing Orbital Images on Ultrafast Time Scales

Following molecular excitation and electron transfer processes in time and space within a single experiment is a long-standing goal of spectroscopy in the field of chemistry. Wallauer et al. combined tomographic photoemission imaging with a femtosecond pump-probe scheme to trace the excited state molecular orbitals of surface-adsorbed molecules with both spatial and temporal resolution. The present demonstration opens a new window for investigating the ultrafast electron transfer dynamics in such processes as chemical reactions on surfaces and intermolecular charge transfers.

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Last Modified: 09.10.2025
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