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Project summaries of area A

Area A aims at developing a comprehensive, fundamental microscopic understanding of the primary processes that lead to light-driven chemical reactions at nanoscale metals based on a set of model systems. The research activities in A therefore concentrate on elementary physical processes in model systems.

The following lists short summaries of the individaul projects in area A.

A01: Understanding and steering nonequilibrium energy flow in metal molecule hybrids at the nanoscale
Carsten Henkel, Matias Bargheer, Henrike Müller-Werkmeister

This project aims at providing an experimental basis for a thorough characterization of the electronic and vibrational heat energy and its transport within nanoscale metals and adjacent molecules including solvents upon optical excitation of the metal. Theoretical modelling will help to bridge ultrafast pump-probe dynamics with stationary non-equilibrium situations for continuous wave excitation, taking into account the quantum nature of the system.

A02: Mechanistic studies of plasmon-induced bond cleavage and cross-coupling reactions using SERS and X-ray probing methods
Ilko Bald, Yan Lu, Renske van der Veen

This project aims at unravelling the mechanism of plasmon-induced carbon-halogen bond cleavage and subsequent carbon-carbon coupling reactions and revealing the influence of the plasmonic material on the observed reactivity. In particular, Au and Au/Pd nanoparticles will be studied as well as alternative plasmonic materials. We employ a unique combination of structurally sensitive probing methods based on surface-enhanced Raman scattering and X-ray spectroscopy, complemented with gas-chromatography mass spectrometry characterisation of reactants and products in solution.

A03: Bond activation and molecular dynamics on metal nanoparticles derived from X-ray spectroscopy
Markus Gühr, Alexander Föhlisch, Peter Saalfrank

This project aims at establishing microscopic governing principles of optically excited selective and efficient reaction pathways of functionalized thiophenols on metal nanoparticles. A stringent, atomic-level description of the elemental reaction steps on their relevant timescales will be developed, from femtoseconds for electronic excitation and relaxation to pico- and nanoseconds for vibrational energy relaxation and intersystem crossings. Soft X-ray spectroscopy yields atomic level sensitivity on orbital occupation, chemical and spin state on all relevant timescales, which is supported by theory using a combination of quantum chemistry and non-adiabatic molecular dynamics.

A04: Steering chemical reactivity by non-local energy transfer via strong light-matter interaction
Wouter Koopman, Henrike Müller-Werkmeister, Carsten Henkel

This project aims to establish a microscopic understanding of energy transfer under vibrational strong coupling (VSC) conditions, to steer chemical reactivity. We suggest that the delocalized nature of vibropolaritons allows manipulating reaction kinetics by opening a channel for long-range energy transfer. This hypothesis will be investigated using advanced Raman micro-spectroscopy techniques and ultrafast transient IR and 2D-IR spectroscopy. The experimental efforts will be complemented by theoretical modelling of the electromagnetic mode landscape and the energy transfer.

A05: Understanding and controlling reactivity under vibrational and electronic strong coupling: Theoretical modelling
Janet Anders, Peter Saalfrank

This project is about using strong coupling (SC) of cavity or plasmonic modes to molecules as a possible new tool in chemistry – with prospects and limitations evaluated by theoretical modelling. Both concrete molecules and unimolecular reactions – ligand dissociation in aryl halides, and photo-switching of molecules – as well as conceptual models will be studied by quantum or quantum-classical methods.

A06: Controlling chemical reactions by propagating surface plasmon polaritons
Svetlana Santer, Kurt Busch, Matias Bargheer

In this project, the potential of propagating surface plasmon polaritons (pSPPs) to influence and steer chemical reactions will be explored. The central idea is to spatially separate the optical excitation of plasmons from the site where the reaction takes place and to study the interplay of light and plasmon fields with reagents in various geometries. Quasi-2D and quasi-1D geometries laterally patterned by nano-lithography, as well as nano-wires and particles will be investigated. Quantitative theoretical modelling of the envisioned structures and effects will guide the selection and optimization of geometries and will provide interpretative support.

A07: Light-induced atomic-scale surface reactivity
Regina Hoffmann-Vogel, Tillmann Klamroth

This project aims at linking the atomic-scale spatial resolution of scanning force microscopy  with the time-resolution of pulsed laser light and to combine both with theoretical simulations, in order to understand the influence of heat, electric fields and hot charge carriers produced by laser pulses on chemical reactivity at metal surfaces. The project will work towards the understanding of the dehydrogenation of polyanthrylene on Au(111) with pulsed laser light, which is known to be induced either by surface heating or STM-injected charge carriers.