Real-Time Chemical Dynamics

Liquid water is a ubiquitous solvent and, as such, is a ubiquitous medium for chemical reactions. The elementary steps underlying these reactions take place on femtosecond time scales, whereas associated reaction kinetics can unfold on time scales that extend to minutes and beyond. Pillar 4 focuses on real-time chemical dynamics in and on liquid water, interrogating and characterizing elementary aqueous-phase processes on their natural femtosecond timescales. One of the central questions that we address is how the ultrafast structural response of water molecules affects the energetics—and, thus, steers the pathways—of chemical reactions in nuclear configuration space. We address this and related questions, e.g., by triggering and tracking the production and interactions of photoexcited solutes, following the dynamics of hydration shells, and interrogating the transient radical species generated by solute and solvent ionisation and/or dissociation. This is achieved by combining experimental techniques such as ultrafast laser technology and state-of-the-art spectroscopies and imaging techniques with theoretical methodologies such as first-principles non-adiabatic molecular-dynamics simulations. Thus, we study aqueous cluster systems, aerosols, droplets, liquid jets, and bulk volumes. In addition to real-time chemical-reaction dynamics in homogenous aqueous solutions, we also employ ultrafast time-resolved methods to develop an understanding of reaction dynamics at aqueous interfaces.

From model systems (e.g., aqueous clusters), aqueous-gas interfaces, to the aqueous bulk, we are studying the following, interconnected water-science challenges:

1. Characterisation of the energetics and dynamics of the transient radicals produced by water and aqueous-solution radiolysis
2. Interrogation of solvation dynamics in water and aqueous solutions, including transient electron, proton, and hydroxide structures and energetics
3. Real-time probing of transient electronic and nuclear structure in ground- and excited-state solvated complexes, including the targeted study of “rare”, reaction-governing events
4. Developing an understanding of ultrafast processes at aqueous interfaces using interfacially sensitive time-resolved probes
5. Implementing electronic, vibrational, and vibronic coherences to control aqueous-phase chemical processes on their natural timescales

 

Pillar IV members

Francesca Calegari, DESY- University of Hamburg  
Contact: francesca.caleagari@desy.de
Expertise/Research interest: Attosecond science & technology, Attosecond Chemistry
Instruments: Few-femtosecond and attosecond sources, charged particle detection, liquid jets

Arno Ehresmann, Institute of Physics, Kassel University  
Contact: ehresmann@physik.uni-kassel.de  
Expertise/Research interest: VUV-VIS photon spectrometry; electron spectrometry; coincidence methods; Molecular dissociation; electron correlations; Energy and charge transfer processes in clusters and liquids  
Instruments: 1m McPherson VUV spectrometer for dispersed-fluorescence spectrometry (40nm - 600 nm); Magnetic bottle electron spectrometer; electron-photon coincidence setup; cluster sources (e.g. water clusters); liquid-jet source;

Kristoffer Haldrup, Technical University of Denmark, Physics Department  
Contact: hald@fysik.dtu.dk  
Expertise/Research interest: Ultrafast; X-ray; Solvation Dynamics; Data Analysis; TR-XSS  

Nils Huse, Department of Physics, University of Hamburg & CFEL  
Contact: nils.huse@uni-hamburg.de  
Expertise/Research interest: ultrafast spectroscopy, reaction dynamics, liquid phase, small and macromolecules  

Ludger Inhester, Center for Free-Electron Laser Science, Deutsches Elektronen-Synchrotron DESY, Hamburg  
Contact: ludger.inhester@cfel.de  
Expertise/Research interest: Electronic-structure Calculations; Ab-initio Molecular Dynamics Simulations; Excited-state Molecular Dynamics; Ultrafast Radiation-induced Chemical Dynamics; Theoretical Modelling of X-ray Spectroscopy  

Thomas Kühne, CASUS/HZDR  
Contact: t.kuehne at hzdr.de  
Expertise/Research interest: Theoretical Chemistry; Computational Physics; Liquid Water; On-Water Catalysis  

Tim Laarmann,  Deutsche Elektronen-Synchrotron DESY  
Contact: tim.laarmann@desy.de  
Expertise/Research interest: ultrafast electron and nuclear dynamics; Attochemistry; solute-solvent interactions; charge motion and energy transfer processes; quantum control using short-pulse lasers; Mid-IR spectromicroscopy   

Robin Santra, DESY & University of Hamburg  
Contact: robin.santra@cfel.de  
Expertise/Research interest: Theoretical atomic, molecular, and optical physics; theoretical chemical physics; computational physics; x-ray-induced processes; ultrafast laser-driven phenomena; applications of short-wavelength free-electron lasers; electronic-structure theory; non-Hermiticity in quantum mechanics

Ruth Signorell, ETH
Contact: ruth.signorell@phys.chem.ethz.ch
Expertise/Research interest: spectroscopic studies of fundamental processes in aerosol particles and clusters
Instruments: Aerosol particles and cluster sources

Stephan Thürmer, Department of Chemistry, Kyoto University  
Contact: thuermer@kuchem.kyoto-u.ac.jp  
Expertise/Research interest: photoelectron spectroscopy;Auger-electron spectroscopy;X-ray spectroscopy;data analysis and instrument control;electron scattering in liquids;charge and energy transfer in aqueous solution;photoelectron angular distributions from liquids;electronic structure of water;  

Florian Trinter, Fritz-Haber-Institut der Max-Planck-Gesellschaft  
Contact: trinter@fhi-berlin.mpg.de  
Expertise/Research interest: Reaction microscope; Liquid microjet; Photoelectron spectroscopy; Synchrotron radiation; Laser system; Adiabatic alignment; Pump-probe experiments; Electronic structure  
Instruments: In collaboration: Liquid-jet photoelectron spectroscopy setup EASI, 
https://doi.org/10.1063/5.0072346

Caterina Vozzi, CNR-IFN  
Contact: caterina.vozzi@cnr.it  
Expertise/Research interest: Ultrafast spectroscopy; attosecond science; photochemistry  
Instruments: HHG-based transient absorption spectroscopy; HHG-based time-resolved photoelectron spectroscopy

Iain Wilkinson, Helmholtz-Zentrum Berlin für Materialien und Energie  
Contact: iain.wilkinson@helmholtz-berlin.de  
Expertise/Research interest: Molecular Dynamics; Ultrafast Spectroscopy; Liquid-Jet Photoemission Spectroscopy  

Bernd Winter, Fritz-Haber-Institut  
Contact: winter@fhi-berlin.mpg.de  
Expertise/Research interest: Liquid water electronic structure; hydration and solute-water interactions; aqueous solution interface;  local and non-local electronic relaxation processes; charge and energy transfer and nuclear dynamics; photoemission; photoelectron circular dichroism from chiral molecules in aqueous solution  
Instruments: EASI setup for liquid-jet photoemission spectroscopy at P04 beamline

 

Speakers: Iain Wilkinson (Helmholtz-Zentrum Berlin) & Ludger Inhester (CFEL/DESY).