Photoionisation-induced switch in aromatic molecule-solvent recognition

该项目旨在对气相中分离的芳香族离子-配体复合物进行红外光谱和量子化学表征，以确定描述电子基态中所涉及的分子间离子-配体相互作用的势能面。靶分子是生物物理相关的基本苯衍生物的阳离子，其被受控数量的中性溶剂分子微溶剂化。在一个合作的努力，两个独特的，但互补的实验策略相结合，以表征分子间的潜力，通过产生集群与两种不同的技术在分子束。第一种方法采用电子碰撞电离的集群生成，这使得表征的全球最小的潜力。在第二种方法中，通过中性前体的共振光电离（REMPI）产生阳离子簇。由于中性和离子簇的相互作用势是定性不同的（由于额外的电荷），较高的躺在本地的最小值的阳离子基态的电位可以填充由REMPI和其特征在于由IR光谱。取决于电离过程中涉及的过剩能量和异构化势垒的大小，局部极小值将向全局极小值异构化。这种电离诱导的异构化过程的动力学将直接通过时间分辨红外光谱测量。的形状的分子间的潜力和这个重组过程的动力学将被调查作为功能的功能基团的取代，参与电离的过剩能量，和微溶剂化的类型和程度。

This project aims at the infrared (IR) spectroscopic and quantum chemical characterization of aromatic ion-ligand complexes isolated in the gas phase, in order to determine the potential energy surface describing the involved intermolecular ion-ligand interaction in the electronic ground state. Target molecules are cations of fundamental benzene derivatives of biophysical relevance, which are microsolvated by a controlled number of neutral solvent molecules. In a collaborative effort, two unique but complementary experimental strategies are combined to characterize the intermolecular potential by generating the clusters with two different techniques in a molecular beam. The first approach employs electron impact ionisation for cluster generation, which enables the characterization of the global minima on the potential. In a second approach, the cation clusters are generated by resonant photoionisation (REMPI) of the neutral precursor. As the interaction potential of the neutral and ionic clusters are qualitatively different (due to the additional charge), higher-lying local minima on the potential of the cation ground state can be populated by REMPI and characterized by IR spectroscopy. Depending on the excess energy involved in the ionisation process and the magnitude of the barrier for isomerisation, the local minima will isomerise toward the global minima. The dynamics of this ionisation-induced isomerisation process will directly be measured by time-resolved IR spectroscopy. The shape of the intermolecular potential and the dynamics of this reorganization process will be investigated as a function of the substitution of functional groups, the excess energy involved in ionisation, and the type and degree of microsolvation.