無秩序反應過程通常不易觀測，特別當事件機率偏低時，經常會被掩蔽而無法察覺。藉著同時紀錄單一分子產生螢光光子的螢光偏振狀態及螢光生命期等訊息，觀察染料分子DiI的無秩序可逆反應過程，包括光誘發構型轉化及環境影響三重態停留時期。當偶發事件不易控制時，單分子螢光計數可有助於暸解這些無秩序反應。

Non-controllable rare events are easily being hidden， thus not easy to monitor. We report the observation of photophysical and photo-chemical reactions of DiI molecules by single molecule fluorescence experiments. By monitoring the polarization and PL lifetime information from individual emission photon， it is possible to distinguish the rare reactions， include photo-induced isomerization， and environmental induced triplet state quenching. Our results demonstrate that single molecule fluorescence measurement is a unique tool for non-controllable reactions.