Experimental Detection of Branching at a Conical Intersection in a Highly Fluorescent Molecule
Experimental Detection of Branching at a Conical Intersection in a Highly Fluorescent Molecule
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DOI：
10.1021/acs.jpclett.5b02476
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发表时间：
2016-01-07
影响因子：
5.7
通讯作者：
Turner, Daniel B.
中科院分区：
文献类型：
--
作者：
Brazard, Johanna;Bizimana, Laurie A.;Turner, Daniel B.
锥形交点是绝热势能面接触的分子构型。它们被预测是普遍存在的，然而凝聚相实验集中在少数具有可忽略的荧光，高光活性或飞秒电子动力学的清晰光谱特征的系统上。虽然罕见，但这些特征已成为圆锥交叉的诊断。在这里，我们在光激发后近两皮秒检测到一个高荧光分子的相干表面交叉事件，该分子没有光活性和纳秒电子动力学。利用亚8fs脉冲获得的高灵敏度测量值的时频分析揭示了由于波包通过锥形相交的分支而引起的信号相移。在模型化合物上演示的时频分析方法将使分子中不表现出其诊断特征的锥形相交的研究成为可能。提高检测圆锥交叉的能力将丰富对其在分子光化学中的机制作用的理解。
Conical intersections are molecular configurations at which adiabatic potential-energy surfaces touch. They are predicted to be ubiquitous, yet condensed-phase experiments have focused on the few systems with clear spectroscopic signatures of negligible fluorescence, high photoactivity, or femtosecond electronic kinetics. Although rare, these signatures have become diagnostic for conical intersections. Here we detect a coherent surface-crossing event nearly two picoseconds after optical excitation in a highly fluorescent molecule that has no photoactivity and nanosecond electronic kinetics. Time frequency analysis of high-sensitivity measurements acquired using sub-8 fs pulses reveals phase shifts of the signal due to branching of the wavepacket through a conical intersection. The time frequency analysis methodology demonstrated here on a model compound will enable studies of conical intersections in molecules that do not exhibit their diagnostic signatures. Improving the ability to detect conical intersections will enrich the understanding of their mechanistic role in molecular photochemistry.