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

分子功能化纳米系统对外界电磁辐射的响应对基础研究和应用都有重要影响。纳米系统中光驱动动力学的洞察力可能会打开许多应用，其中分子吸附反应的加强和控制起着核心作用。尽管气溶胶吸引了相当大的兴趣，特别是在大气物理或健康应用方面，成像分子吸附在这种孤立粒子上的近场诱导光反应仍然具有挑战性。我们最近推出的反应纳米显微镜，依靠对从辐照的纳米粒子表面逃逸的电子和带电分子片段的符合检测，克服了这些挑战。在这个项目中，我们将通过执行亚飞秒双色控制和泵浦探测实验来显著扩展这项技术的范围，以使用更先进的反应纳米显微镜来研究纳米粒子上的解离动力学。计划中的电子-离子和(散射)光子符合研究将由现有的100千赫重复频率低周期中红外激光系统实现，其中将增加一个双色合成器。我们将通过双色脉冲方案在纳米尺度上实现亚周期电子动力学的时空操纵，从而允许定制纳米颗粒表面的光学近场。此外，部署在更长时间尺度上的泵浦-探测器研究将有助于揭示核动力学。我们还将研究金属和介电金属核壳纳米粒子，以阐明等离子体共振对这些吸附分子中超快动力学的影响。量子和半经典模拟的发展和实施将有助于对测量数据的分析和解释。这项联合的实验和理论工作旨在揭示小分子在纳米颗粒上光诱导化学反应的动力学机制，包括键断裂、质子迁移以及带电分子碎片的产生和发射。

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.