Optical spatio-temporal optical control of electron-induced processes at graphene-supported metal cluster nano-structures

在这个方案中，我们希望探索利用整形超快激光脉冲来优化控制金属纳米团簇阵列中电磁场的可能性，该阵列由石墨烯支撑的尺寸选择的银团簇组成，从几个原子扩展到纳米尺度。到目前为止，我们对这种阵列的光学性质一无所知，我们预计还会发现有趣的新现象，特别是因为2D材料石墨烯具有耐人寻味的电子倾向。石墨烯被用作衬底来提供几何模板，即定义团簇距离-它还提供团簇之间的电子耦合的潜力将是研究的主题。我们将使用尺寸选择的团簇来获得完美的单分散样品，并研究从离散电子团簇结构到等离子体电子团簇结构的转变对场局域化可能性的影响。光激励将由调制(频率、相位、偏振)超快激光脉冲提供。在一种新的实验方法中，将通过检测物理吸附分子(CH3Br，CH3Cl)在金属团簇上的电子发射诱导解离的有效性来探索电磁场局域化的影响。因此，在控制回路中使用分子碎片(CH3)质量信号作为反馈信号，以获得最佳电磁场。场局域化的研究将通过扫描隧道微观检测金属团簇卤化的空间范围作为参数团簇大小和团簇间距的函数。

In this proposal we wish to explore the potential of optimal control with shaped ultrafast laser pulses to localize the electromagnetic field in metal nano-cluster arrays consisting of graphene-supported size-selected silver clusters with extensions from a few atoms to the nanometer scale. Nothing is known so far about the optical properties of such arrays and we expect to find interesting new phenomena in particular also because of the intriguing electronic propensities of the 2D-material graphene. Graphene is employed as a substrate to provide a geometric template, i.e., to define the cluster distances – its potential to also provide electronic coupling between the clusters will be a subject of investigation. Size-selected clusters will be employed to obtain perfectly monodisperse samples and to investigate the effect of the transition from discrete to plasmonic electronic cluster structure on the possibility of field localization. Optical excitation will be provided by modulated (frequency, phase, polarization) ultrafast laser pulses. In a new experimental approach, the effect of the electromagnetic field localization will be probed by detecting the effectiveness of the electron-emission-induced dissociation of physisorbed adsorbate molecules (CH3Br, CH3Cl) on the metal clusters. Thus, the molecular fragment (CH3) mass signal will be employed as feedback signal in the control loop to obtain the optimal electromagnetic field. The investigation of the field localization will be performed by scanning tunnelling microscopic detection of the spatial extent of the metal cluster halogenation as a function of the parameters cluster size and cluster separation.