Vibronic coherence evolution in multidimensional ultrafast photochemical processes
Vibronic coherence evolution in multidimensional ultrafast photochemical processes
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DOI：
10.1038/s41467-019-13503-9
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发表时间：
2019-12-09
影响因子：
16.6
通讯作者：
Khalil, Munira
中科院分区：
文献类型：
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作者：
Gaynor, James D.;Sandwisch, Jason;Khalil, Munira
光激发分子用于有效传递能量的电子、振动和振动耦合的复杂编舞是引人注目的，但对控制这些过程的时间演化的振动状态的明确描述已被实验证明是难以捉摸的。我们使用多维电子-振动光谱来识别特定的时间依赖的激发态振动耦合，涉及多个电子态，高频振动和低频振动，这些振动参与了光激发过渡金属配合物的超快系统间穿越和随后的弛豫。我们发现了一种驱动长寿命电荷分离的激发态振动机制，该机制由一个初始的电子局域振动波包组成，该波包在传播约600飞秒后触发离域到两个电荷转移态。电子离域通过由50厘米（-1）耦合驱动的非绝热内部转换发生，导致持续时间约为1皮秒的振动相干转移。这项研究展示了多维电子振动光谱在阐明涉及多个分子坐标的复杂的、非平衡的能量和电荷转移机制方面的力量。
The complex choreography of electronic, vibrational, and vibronic couplings used by photoexcited molecules to transfer energy efficiently is remarkable, but an unambiguous description of the temporally evolving vibronic states governing these processes has proven experimentally elusive. We use multidimensional electronic-vibrational spectroscopy to identify specific time-dependent excited state vibronic couplings involving multiple electronic states, high-frequency vibrations, and low-frequency vibrations which participate in ultrafast intersystem crossing and subsequent relaxation of a photoexcited transition metal complex. We discover an excited state vibronic mechanism driving long-lived charge separation consisting of an initial electronically-localized vibrational wavepacket which triggers delocalization onto two charge transfer states after propagating for similar to 600 femtoseconds. Electronic delocalization consequently occurs through nonadiabatic internal conversion driven by a 50 cm(-1) coupling resulting in vibronic coherence transfer lasting for similar to 1 picosecond. This study showcases the power of multidimensional electronic-vibrational spectroscopy to elucidate complex, non-equilibrium energy and charge transfer mechanisms involving multiple molecular coordinates.