Department of Chemistry and Biochemistry, The Ohio State University, Columbus, Ohio 43210, United States.
J Phys Chem A. 2020 Aug 6;124(31):6356-6362. doi: 10.1021/acs.jpca.0c06307. Epub 2020 Jul 28.
Femtosecond stimulated Raman spectroscopy (FSRS) is an ultrafast pump-probe technique designed to elucidate excited-state molecular dynamics by means of vibrational spectroscopy. We present a first-principles protocol for the simulation of FSRS that integrates molecular dynamics with computational resonance Raman spectroscopy. Theoretical calculations can monitor the time-dependent evolution of specific vibrational modes and thus provide insight into the nature of the motion responsible for the experimental FSRS signal, and we apply this technique to study quaterthiophene derivatives. The S state of two different quaterthiophene derivatives relaxes via in-phase and out-of-phase stretching modes whose frequencies are coupled to the dihedral backbone angle, such that the spectral evolution reflects the excited-state relaxation toward a planar conformation. The simulated spectra aid in confirming the experimental assignment of the vibrational modes that are probed in the existing FSRS experiments on quaterthiophenes.
飞秒受激拉曼光谱（FSRS）是一种超快泵浦探测技术，旨在通过振动光谱阐明激发态分子动力学。我们提出了一种用于 FSRS 模拟的从头算方案，该方案将分子动力学与计算共振拉曼光谱相结合。理论计算可以监测特定振动模式的时变演化，从而深入了解导致实验 FSRS 信号的运动的本质，我们将该技术应用于研究四噻吩衍生物。两种不同的四噻吩衍生物的 S 态通过同相和异相伸缩模式弛豫，其频率与二面角主链角耦合，使得光谱演化反映了激发态向平面构象的弛豫。模拟光谱有助于证实现有 FSRS 实验中探测到的振动模式的实验分配。
