Institute of Physical and Theoretical Chemistry, Goethe University Frankfurt, Max-von-Laue-Str. 7, 60438 Frankfurt, Germany.
Departamento de Química Física, Universidad de Murcia, E-30071 Murcia, Spain.
J Chem Phys. 2017 Oct 28;147(16):164116. doi: 10.1063/1.4999455.
Vibrationally resolved electronic absorption spectra including the effect of vibrational pre-excitation are computed in order to interpret and predict vibronic transitions that are probed in the Vibrationally Promoted Electronic Resonance (VIPER) experiment [L. J. G. W. van Wilderen et al., Angew. Chem., Int. Ed. 53, 2667 (2014)]. To this end, we employ time-independent and time-dependent methods based on the evaluation of Franck-Condon overlap integrals and Fourier transformation of time-domain wavepacket autocorrelation functions, respectively. The time-independent approach uses a generalized version of the FCclasses method [F. Santoro et al., J. Chem. Phys. 126, 084509 (2007)]. In the time-dependent approach, autocorrelation functions are obtained by wavepacket propagation and by the evaluation of analytic expressions, within the harmonic approximation including Duschinsky rotation effects. For several medium-sized polyatomic systems, it is shown that selective pre-excitation of particular vibrational modes leads to a redshift of the low-frequency edge of the electronic absorption spectrum, which is a prerequisite for the VIPER experiment. This effect is typically most pronounced upon excitation of modes that are significantly displaced during the electronic transition, such as ring distortion modes within an aromatic π-system. Theoretical predictions as to which modes show the strongest VIPER effect are found to be in excellent agreement with experiment.
为了解释和预测在振动促进电子共振（VIPER）实验中探测到的振子跃迁，我们计算了包括振动预激发效应的振动分辨电子吸收光谱。为此，我们分别采用基于 Franck-Condon 重叠积分评估和时域波包自相关函数傅里叶变换的时间无关和时间相关方法。时间无关方法使用 FCclasses 方法的广义版本[F. Santoro 等人，J. Chem. Phys. 126, 084509（2007）]。在时间相关方法中，自相关函数是通过波包传播和在包括 Duschinsky 旋转效应的谐波近似下评估解析表达式获得的。对于几个中等大小的多原子体系，我们表明，对特定振动模式的选择性预激发导致电子吸收光谱低频边缘的红移，这是 VIPER 实验的前提。这种效应通常在电子跃迁过程中发生明显位移的模式（例如芳香π系统中的环变形模式）的激发时最为明显。理论预测哪些模式表现出最强的 VIPER 效应，与实验结果非常吻合。
