Multi-Exciton Dynamics in Molecular Nano-Hybrid Systems

揭示分子系统中能量传递过程的细节一直是人们感兴趣的问题。光电电池或发光二极管中电子激发能量转移的技术重要性代表了这种趋势的一个原因。多激子产生、激子裂变和聚变以及金属纳米结构或微腔光子等等离子激元激发的杂化态形成等新现象是另一个原因。为了探索这种新现象，不同分子同时受到更强光激发的特定区域将成为理论项目工作的重点。因此，我们将利用并进一步发展多电子理论来研究单分子或分子二聚体的光诱导反应。应采用不同的基于波函数的方法。对于更大的分子复合物，将引入多激子方法，并推导非线性动力学方程。因此，在高激发态分子（主要是在苝或对六苯基分子体系中）聚集的地方，应研究超快的激发能转移光诱导过程。大量的非线性和部分相干的能量传递过程的微观描述将被实现，特别是在它们依赖于光激发的强度和持续时间和超越标准激子-激子湮灭的制度。对于分子二聚体，采用多电子方法进行基准计算，验证了同一体系中多激子描述所得结果的重要性。进一步给出了多激子理论所需的能量和耦合矩阵元素。为了弥补动力学方程的正式推导和光谱实验之间的差距，我们将计算，例如，发射和瞬态吸收光谱。除了研究孤立的分子复合物外，我们还将考虑放置在分子附近的金属纳米粒子的等离子激元激发的影响。将演示多激子动力学的一种特殊控制。进入一个新的研究领域将是考虑分子系统放置在微腔。根据文献的建议，我们将研究腔光子辅助激发分子间能量转移的新机制的形成。

It is of ongoing interest to uncover details of energy transfer processes in molecular systems. The technological importance of electronic excitation energy transfer in photovoltaic cells or light emitting diodes represents one reason for this tendency. Novel phenomena like multiple exciton generation, exciton fission and fusion as well as hybrid state formation with plasmon excitations of metal nano-structures or microcavity photons constitutes another reason. In order to explore such novel phenomena the particular regime of stronger optical excitation where different molecules are excited simultaneously will be in the focus of theoretical project work.Therefore, we will utilize and further develop a many-electron theory to study the photoinduced response of a single molecule or a molecular dimer. Different wave function based methods shall be applied. Turning to larger molecular complexes a multi-exciton approach will be introduced and nonlinear kinetic equations will be derived. With that ultrafast photoinduced processes of excitation energy transfer shall be studied where higher excited molecular electronic states become populated (mainly in systems of perylen or para-sexiphenyl molecules). A microscopic description of a multitude of nonlinear and partially coherent energy transfer processes shall be achieved, in particular in their dependence on intensity and duration of optical excitation and beyond the regime of standard exciton-exciton annihilation. Concerning the molecular dimer the benchmark computations within the many-electron approach are used to validate the importance of those results obtained with the multi-exciton description for the same system. Further-on, energies and coupling matrix elements needed for the multi-exciton theory are offered. To bridge the gap between the formal derivation of kinetic equations and spectroscopic experiments we will calculate, for example, emission and transient absorption spectra.Besides the study of isolated molecular complexes we will also account for effects of plasmon excitations of metal nano-particles placed in the vicinity of the molecules. A particular control of the multi-exciton dynamics shall be demonstrated. A step into a novel research area will be the consideration of molecular systems placed in a microcavity. Following suggestions from literature we will investigate the formation of new regimes of cavity photon assisted excitation energy transfer among the molecules.