Determination of the energetic position of electronically excited states, their structures and life times

孤立的分子系统在其基态和电子激发态的永久偶极矩将使用电子斯塔克光谱测定。我们的目标是阐明各种问题。首先，我们试图了解不同配体的取代位置与不同的电子效应对发色团的影响。光子的吸收可能导致偶极矩的大的变化，这取决于激发态。最低激发单重态的偶极矩由于它们不同的电子分布而有很大的不同。因此，这些态的电子性质可以从偶极矩的大小和方向来阐明，除了永久偶极矩外，跃迁偶极矩的大小和方向对电子激发态的分类也很重要。跃迁偶极矩的方向对于福斯特能量转移是重要的，在这种情况下，供体和受体的取向不是通过柔性连接体统计分布的。光谱技术，这是能够确定的过渡偶极矩的方向，一般工作与定向分子。取向不一定是宏观的，如关于分子固定轴与跃迁偶极矩轴的扭转的量子干涉效应所示。我们提出了一个实验中，定向参考系统的永久偶极矩在两个电子状态的轴。在新的装置中，对场强高达10 kV/cm的光谱进行了模拟，结果表明，这种效应足够大，可以观察到。利用垂直排列的线偏振光，使我们能够在不同的选择规则之间切换。我们可以证明，这是如何提高偶极矩测定的准确性的。用四分之一波片交换用于旋转线偏振光的半波片，我们能够在右圆偏振光和左圆偏振光之间切换。它们在Stark光谱中表现出不同的选择规则，并允许Stark光谱中对映体的区分。最后，电子Stark光谱将用于确定不同推拉系统的偶极矩。我们将把主要注意力放在系统中，供体和受体位于不同的共价桥生色团。这些系统可以作为分子开关，通过其大的偶极矩变化吸收光子。

Permanent dipole moments of isolated molecular systems in their ground and electronically excited states will be determined using electronic Stark spectroscopy. We aim to shed light on various problems. First, we seek to understand the influence of the substitution position of different ligands with varying electronic effects on the chromophore. Absorption of a photon may lead to large changes of the dipole moments, depending on the excited state. The dipole moments of the lowest excited singlet states differ considerably due to their differing electron distribution. Thus, the electronic nature of these states can be elucidated from the size and direction of the dipole moments.Apart from permanent dipole moments the size and directions of the transition dipole moment are important for the classification of electronically excited states. The direction of the transition dipole moment is important for Förster energy transfer, in cases, in which the orientations of the donor and acceptors are not distributed statistically through flexible linkers. Spectroscopic techniques, which are capable of determining the direction of the transition dipole moment in general work with oriented molecules. The orientation does not have to be macroscopic, as quantum interference effects of torsions about molecule fixed axes with the transition dipole moment axis show. We propose an experiment in which the oriented reference system are the axes of the permanent dipole moments in both electronic states. Simulations of the spectra with filed strength of up to 10 kV/cm as can be reached in the new set-up show that the effect is large enough to be observed.Utilization of linearly polarized light in a perpendicular arrangement enables us to switch between different sets of selection rules. We could show, how this enhances the accuracy of dipole moment determinations. Exchange of the half wave plate used to rotate the linearly polarized light by a quarter wave plate we are able to switch between right and left circular polarized light. They show different selection rules in the Stark spectra and allow for a differentiation of enantiomers in the Stark spectra.Finally, electronic Stark spectroscopy will be used to determine the dipole moments of different push-pull systems. We will put the main attention to systems in which donor and acceptor are located in different covalently bridged chromophores. These systems may act as molecular switches through their large dipole moment changes upon absorption of a photon.