Excitonic and vibronic couplings in weakly bound molecular aggregates

分子聚集体的理论描述往往依赖于单个组分及其相互作用的使用。对于大型系统，这通常是唯一可行的方法，然而，对于较小的系统，可以通过超分子方法进行补充，其中聚集体被视为一个整体。在第一个资助期内，这种综合策略已成功地用于分析-与S。Leutwyler，伯尔尼大学-在一系列氢键分子二聚体中激子能量分裂的所谓淬灭。此外，对于两个系统的激发光谱可以很好地再现在整个光谱范围内。在新的供资期内，调查将扩大到具有不同类型互动的其他系统，以探索所用方法的普遍性。这包括在电子基态或激发态具有较低对称性的系统，以及部分氘代的二聚体，其中整体对称性被核质量的不对称分布破坏。作为一个新的工作重点，猝灭和振动相互作用（振动激发）的电子激发能的转移的影响进行了研究。预计这将因所讨论的猝灭效应而减慢，并且由于同时振动激发，还应该表现出更复杂的时间依赖性。这两个问题都有待证实，并更加量化。最后，如果时间允许，应尝试扩展到更大的骨料，特别是三聚体。

The theretical description of molecular aggregates often relies on the use of the individual components and their interactions. For large systems this is often the only viable approach which can, however, for smaller systems be complemented by a supermolecular approach, where the aggregate is considered as a whole. In the first funding period this combined strategy has been successfully employed to analyse - in cooperation with the experimental group of Prof. S. Leutwyler, Univ. Bern - the so-called quenching of the excitonic energy splitting in a series of hydrogen-bonded molecular dimers. In addition, for two systems the excitation spectra could be well reproduced in the whole spectral range. In the new funding period the investigations are to be extended to other systems with different types of interaction to explore the generality of the methods applied. This comprises systems with lower symmetry in the electronic ground or excited state and furthermore partially deuterated dimers where the overall symmetry is broken by the asymmetric distribution of the nuclear masses. As a new focus of the work, the impact of the quenching and vibronic interactions (vibrational excitation) on the transfer of the electronic excitation energy is to be investigated. This is expected to be slowed down by the quenching effect in question and also should exhibit a more complex time dependence owing to the simultaneous vibrational excitation. Both is to be confirmed and made more quantitative. Finally and if time permits, an extension to larger aggregates, especially trimers, shall be attempted.