Fedunov Roman G, Plotnikova Anastasiia V, Ivanov Anatoly I, Vauthey Eric
Volgograd State University , University Avenue 100, Volgograd 400062, Russia.
Department of Physical Chemistry, University of Geneva , 30 quai Ernest-Ansermet, CH-1211 Geneva 4, Switzerland.
J Phys Chem A. 2017 Jan 19;121(2):471-481. doi: 10.1021/acs.jpca.6b11581. Epub 2017 Jan 6.
A model for simulating the transient electronic absorption spectra of donor-acceptor dyads undergoing ultrafast intramolecular charge transfer in solution has been developed. It is based on the stochastic multichannel point-transition approach and includes the reorganization of high-frequency intramolecular modes (treated quantum mechanically) and of low frequency intramolecular and solvent modes (described classically). The relaxation of the slow modes is assumed to be exponential with time constants taken from experiments. The excited-state dynamics is obtained by simulating the population distribution of each quantum state after optical excitation and upon electronic and vibrational transitions. This model was used to simulate the transient electronic absorption spectra measured previously with a pyrylium phenolate in acetonitrile. A very good agreement between the simulated and measured spectra was obtained assuming a three-level model including the ground state, the optically excited state, and a dark state with large charge-transfer character and a substantially different geometry relative to that of the optically excited state. The merit of this approach to disentangle the contributions of both population changes and relaxation processes to the ultrafast spectral dynamics will be discussed.
已开发出一种用于模拟供体-受体二元体系在溶液中进行超快分子内电荷转移时的瞬态电子吸收光谱的模型。该模型基于随机多通道点跃迁方法，包括高频分子内模式（采用量子力学处理）以及低频分子内和溶剂模式（采用经典描述）的重组。慢模式的弛豫假定为指数形式，时间常数取自实验。通过模拟光激发后以及电子和振动跃迁后每个量子态的布居分布来获得激发态动力学。该模型用于模拟先前在乙腈中用酚盐吡喃鎓测得的瞬态电子吸收光谱。假设一个三能级模型，包括基态、光激发态以及具有大电荷转移特征且相对于光激发态几何结构有显著差异的暗态，模拟光谱与测量光谱之间取得了很好的一致性。将讨论这种方法在区分布居变化和弛豫过程对超快光谱动力学贡献方面的优点。
