Intra- and Intermolecular Dynamics of pi-conjugated molecules and their dimers

这个项目的中心是与材料科学相关的多环芳烃和杂环。我们将研究这些分子在光激发后发生的过程。大多数实验将在气相进行，但补充研究将在溶液中进行。除了孤立的分子外，我们还将研究它们的二聚体，以更好地理解大聚集体的能量传递过程。气相数据可以与高度精确的计算结果进行比较，从而为更大集合体的理论提供了有价值的基准。在这个项目中最相关的实验方法将是皮秒时间分辨光谱。此外，我们希望在项目的这个阶段建立使用电子成像检测的时间分辨光电子能谱。一类重要的分子成为我们研究计划的重点是有机杂环，如1,8-萘酸酐（NDCA）和1,8-萘酰亚胺（NI）。这些分子在ps时间尺度上表现出内部转化和系统间交叉的竞争。对这些模型系统中竞争的详细描述将有助于更好地理解杂环的光致动力学。此外，我们将继续在芘上的工作，并研究作为激发能和取代基化学性质的函数的准分子的形成。另一个令人感兴趣的系统是四烯二聚体，它构成了单线态裂变的模型系统。在此过程中，一个激发态失活为两个三重态，这被认为是光电材料中能量转移的有效途径。最后，我们将探讨应变环的结构和动力学，这是碳结构缺陷的模型。我们注意到，与本部门理论和筹备小组的密切合作对这项建议特别重要。

In the center of this project are polycyclic aromatic hydrocarbons and heterocycles that are of relevance in material science. We will study the processes that occur in these molecules after photoexcitation. The majority of experiments will be carried out in the gas phase, but complementary studies will be conducted in solution. Beside the isolated molecules we will also study their dimers to better understand energy transfer processes in larger aggregates. Gas-phase data allow a comparison with the results of highly accurate computations and thus provide a valuable benchmark for the theory on larger aggregates. The most relevant experimental method in this project will be picosecond time-resolved spectroscopy. In addition we want to establish time-resolved photoelectron spectroscopy using imaging detection of electrons in this phase of the project. An important class of molecules that moved into the focus of our research program are organic heterocycles like 1,8-naphthalic anhydride (NDCA) and 1,8-naphthalimide (NI). These molecules exhibit a competition between internal conversion and intersystem crossing on a ps-timescale. A detailed description of the competition in these model systems will contribute to a better understanding of the photoinduced dynamics in heterocycles in general.Furthermore we will continue the work on pyrene and study the formation of excimers as a function of excitation energy and of the chemical character of the substituent. Another system of interest is the tetracene dimer, which constitutes a model system for singlet fission. In this process an excited singlet state deactivates to two triplet states, which is proposed to be an efficient route for energy transfer in optoelectronic materials. Finally we will explore the structure and dynamics of strained rings, which are models for defects in carbon structures.We note that the close cooperation with theoretical and preparative groups at our department is of particular importance for this proposal.