The photophysical processes of singlet fission and triplet fusion have numerous emerging applications. They involve the separation of a photo-generated singlet exciton into two dark triplet excitons and the fusion of two dark triplet excitons into an emissive singlet exciton, respectively. The role of the excimer state and the nature of the triplet-pair state in these processes have been a matter of contention. Here we analyse the room temperature time-resolved emission of a neat liquid singlet fission chromophore and show that it exhibits three spectral components: two that correspond to the bright singlet and excimer states and a third component that becomes more prominent during triplet fusion. This spectrum is enhanced by magnetic fields, confirming its origins in the recombination of weakly coupled triplet pairs. It is thus attributed to a strongly coupled triplet pair state. These observations unite the view that there is an emissive intermediate in singlet fission and triplet fusion, distinct from the broad, unstructured excimer emission.

单线态裂变和三线态聚变的光物理过程有许多新兴应用。它们分别涉及将光生单线态激子分离成两个暗三线态激子以及将两个暗三线态激子融合成发射性单线态激子。准分子态的作用和三重态对态的性质在这些过程中一直是一个有争议的问题。在这里，我们分析了纯液体单线态裂变发色团的室温时间分辨发射，并表明它表现出三个光谱成分：两个对应于明亮的单线态和准分子态，第三个成分在三线态融合过程中变得更加突出。该光谱通过磁场增强，证实了其起源于弱耦合三重态对的重组。因此，它归因于强耦合的三重态对状态。这些观察结果统一了这样的观点：单重态裂变和三重态聚变中存在发射中间体，与广泛的非结构化准分子发射不同。