Nazari M, Bösch C D, Rondi A, Francés-Monerris A, Marazzi M, Lognon E, Gazzetto M, Langenegger S M, Häner R, Feurer T, Monari A, Cannizzo A
Institute of Applied Physics, University of Bern, Switzerland.
Department of Chemistry and Biochemistry, University of Bern, Switzerland.
Phys Chem Chem Phys. 2019 Aug 21;21(31):16981-16988. doi: 10.1039/c9cp03147b. Epub 2019 Jul 25.
In this study we reveal the detailed photocycle of a phenanthrene monomer. Phenanthrene serves as a popular building block for supramolecular systems and as an archetypal molecule to study the photochemistry of polycyclic aromatic hydrocarbons. By means of femtosecond time-resolved UV-vis transient absorption spectroscopy and molecular modeling, we found that the first bright transition involves the second excited singlet state, which relaxes toward the lowest excited singlet state with a biphasic internal conversion through a conical intersection region: a fast coherent branching followed by an exceptionally slow (∼ps) incoherent internal conversion. We succeeded to pinpoint the complete relaxation pathways and to extract the relevant parameters, e.g., the branching ratio at the conical intersection and internal conversion rates.
在本研究中，我们揭示了菲单体的详细光循环。菲是超分子体系中常用的结构单元，也是研究多环芳烃光化学的典型分子。通过飞秒时间分辨紫外可见瞬态吸收光谱和分子模拟，我们发现第一个明亮跃迁涉及第二激发单重态，它通过一个锥形交叉区域以双相内转换的方式向最低激发单重态弛豫：先是快速的相干分支，随后是异常缓慢（约皮秒）的非相干内转换。我们成功确定了完整的弛豫途径并提取了相关参数，例如锥形交叉处的分支比和内转换速率。
