Study on Microscopic Solvation Effects on Nonradiative Processes

本研究项目旨在通过对含芳香发色团的溶剂化团簇的实验研究，阐明芳香分子中的非辐射过程如何以及为什么受到周围溶剂的影响。通过应用多种光谱学方法，如多重激光共振、质量选择光电离和超快激光光谱学，取得了以下结果：研究了吖啶和9-吖啶酮的水合簇，以探索氢键网络结构基序与发色团非辐射过程之间的分子水平相关性。通过比较实验数据（电子跃迁和荧光探测红外光谱中的能带位移）和密度泛函理论计算，确定了水合物的几何形状。皮秒时间分辨测量表明，荧光寿命在很大程度上取决于簇大小以及氢键位点。微观上的溶剂化效应已经从密切相关的（n, π^*）和（π, π^*）态的能量学角度得到了解释，这两个态的特征是被氢键移动。重新研究了单体S_1-S_0区苯簇的电子跃迁。通过对不同同位素二聚体和三聚体离子通道记录的质量选择性孔洞谱的详细检查，发现过去二十年来被接受的尺寸分配需要纠正。对苯的三聚体和四聚体提出了新的赋值，解决了目前报道的实验结果与理论结果之间的矛盾。目前的数据还提供了簇的几何和激发交换相互作用的信息。用皮秒时间分辨泵浦探针耗尽旋转相干光谱法测定了含9-氰蒽溶剂化团簇的几何结构。特别是首次建立了二氧化碳、乙腈、氟仿等非质子溶剂分子的结构基序，为探讨相关氰基芳烃簇中反应动力学与溶剂化结构之间的关系奠定了坚实的基础。少

The present research project aims to clarifying how and why nonradiative processes in aromatic molecules are influenced by solvents surrounding them through experimental investigations on solvated clusters containing aromatic chromophores. By applying various spectroscopic methods, i.e., multiple laser resonances, massselective photoionization, and ultrafast laser spectroscopy, the following results have been achieved.1.Hydrated clusters of acridine and 9-acridone have been studied to explore molecular-level correlation between structural motifs in hydrogen-bonding networks and nonradiative processes in the chromophores. Geometries of the hydrates have been determined by comparison of experimental data(band shifts in electronic transitions and fluorescence-detected infrared spectra)with density-functional-theory calculations. Pico-second time-resolved measurements have shown that fluorescence lifetimes depend substantially on cluster sizes as well as hydrogenbonding sites. The microsco … More pic solvation effects have been explained in terms of energetics relating to closely lying(n, π^*)and(π, π^*)states, which are characteristically shifted by hydrogen bonds.2.Electronic transitions of benzene clusters in the monomer S_1-S_0 region have been reinvestigated. It has been found that previous size-assignments accepted for two decades need to be corrected, based on detailed examination of mass-selective holeburing spectra recorded for various isotopic species of dimer and trimer ion channels. New assignments have been proposed for the benzene trimer and tetramer, which resolve contradictions between experimental and theoretical results reported so far. The present data also provide information on geometry and excitation exchange interactions of the clusters.3.Geometrical structure of solvated clusters containing 9-cyanoanthracene has been determined by rotational coherence spectroscopy implemented with pico-second time-resolved pump-probe depletion. In particular, structral motif for aprotic solvent molecules, e.g., carbon dioxide, acetonitrile, and fluoroform, has been established for the first time, which will be a solid foundation for discussing the relationship between reaction dynamics and solvation structure in clusters of related cyano-aromatics. Less