Deng Gang-Hua, Qian Yuqin, Li Xia, Zhang Tong, Jiang Wei, Harutyunyan Avetik R, Chen Gugang, Chen Hanning, Rao Yi
Department of Chemistry and Biochemistry, Utah State University, Logan, Utah 84322, United States.
Beijing National Laboratory for Molecular Sciences and State Key Laboratory of Molecular Reaction Dynamics, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, China.
J Phys Chem Lett. 2021 Apr 1;12(12):3142-3150. doi: 10.1021/acs.jpclett.1c00397. Epub 2021 Mar 23.
Vibronic coupling is believed to play an important role in siglet fission, wherein a photoexcited singlet exciton is converted into two triplet excitons. In the present study, we examine the role of vibronic coupling in singlet fission using polarized transient absorption microscopy and simulations on single-crystalline pentacene. It was found that singlet fission in pentacene is greatly facilitated by the vibrational coherence of a 35.0 cm phonon, where anisotropic coherence persists extensively for a few picoseconds. This coherence-preserving phonon that drives the anisotropic singlet fission is made possible by a unique cross-axial charge-transfer intermediate state. In the same fashion, this phonon was also found to predominantly drive the quantum decohence of a correlated triplet pair to form a decoupled triplet dimer. Moreover, our transient kinetic experimental data illustrates notable directional anisotropicity of the singlet fission rate in single-crystalline pentacene.
人们认为，振子耦合在单线态裂变中起着重要作用，在单线态裂变过程中，一个光激发单线态激子会转化为两个三线态激子。在本研究中，我们使用偏振瞬态吸收显微镜和对单晶并五苯的模拟来研究振子耦合在单线态裂变中的作用。研究发现，35.0厘米声子的振动相干极大地促进了并五苯中的单线态裂变，其中各向异性相干在几皮秒内广泛持续。驱动各向异性单线态裂变的这种保持相干的声子是由一种独特的交叉轴电荷转移中间态实现的。同样，还发现这种声子主要驱动相关三线态对的量子退相干，以形成解耦的三线态二聚体。此外，我们的瞬态动力学实验数据表明单晶并五苯中单线态裂变速率存在显著的方向各向异性。
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