Singlet fission (SF) is a spin‐allowed conversion process, in which one singlet exciton is replaced by a pair of triplet excitons resided on adjacent molecules. To rationalize this phenomenon, a multiexcitonic spin‐zero triplet‐pair state is generally hypothesized as an intermediate state for SF. However, the details of its formation during the fission process, and its subsequent evolution over time are still remain unclear. Thus, this work provides a model of the SF system for triisopropylsilylethynyl‐pentacene by using femtosecond time‐resolved transient absorption spectroscopy. A mixed state of singlet and multiexciton, which mediates the ultrafast SF process is directly observed. This work represents a new viewpoint for the research on SF intermediates.

中文翻译：

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三异丙基甲硅烷基乙炔基并五苯中单线态裂变的多激子态

单重态裂变（SF）是自旋允许的转化过程，其中一个单重态激子被一对相邻分子上的三重态激子所取代。为了使这种现象合理化，通常将多激子自旋零三重态对状态假设为SF的中间状态。然而，在裂变过程中其形成的细节及其随时间的演变仍不清楚。因此，这项工作通过使用飞秒时间分辨瞬态吸收光谱法提供了三异丙基甲硅烷基乙炔基-并五苯的SF系统模型。直接观察到介导超快SF过程的单重态和多激态的混合状态。这项工作代表了SF中间体研究的新观点。