Near-field-controlled strong-field physics in molecules on nanoparticle surfaces

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The response of molecule-functionalized nanosystems to external electromagnetic radiation has impact in both fundamental research as well as its applications. The insights in light-driven dynamics in nanosystems may open up many applications, in which the enhancement and control of molecular adsorbate reactions play a central role. Despite considerable interest attracted by aerosols, in particular in atmospheric physics or health applications, imaging near-field induced photo-reactions of molecular adsorbates on such isolated particles has remained challenging. Reaction nanoscopy, recently introduced by us, which relies on the coincident detection of electrons and charged molecular fragments escaping from the irradiated nanoparticle surface, overcomes these challenges. In this project, we will extend substantially the scope of this technique by performing sub-femtosecond two-color control and pump-probe experiments to investigate the dissociation dynamics on nanoparticles with a more advanced reaction nanoscope. The planned electron-ion and (scattered) photon coincidence studies will be enabled by an available 100 kHz repetition rate few-cycle mid-infrared laser system, to which a two-color synthesizer will be added. We will achieve spatiotemporal steering of sub-cycle electronic dynamics at the nanoscale with two-color pulse schemes allowing the tailoring of the optical near-fields on the nanoparticle surface. Furthermore, pump-probe studies deployed into longer timescales will shed light on the nuclear dynamics. We will also study metallic and dielectric-metallic core-shell nanoparticles to elucidate the influence of plasmonic resonances on the ultrafast dynamics in these adsorbate molecules. The analysis and interpretation of the measured data will be aided by the development and implementation of quantum and semi-classical simulations. The joint experimental and theoretical work aims at uncovering the mechanisms governing the dynamics of light-induced chemical reactions of small molecules on nanoparticles, including bond breaking, proton migration, as well as creation and emission of charged molecular fragments.