Revealing electronic state-switching at conical intersections in alkyl iodides by ultrafast XUV transient absorption spectroscopy
Revealing electronic state-switching at conical intersections in alkyl iodides by ultrafast XUV transient absorption spectroscopy
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DOI：
10.1038/s41467-020-17745-w
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发表时间：
2020-08-12
影响因子：
16.6
通讯作者：
Leone, Stephen R.
中科院分区：
文献类型：
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作者：
Chang, Kristina F.;Reduzzi, Maurizio;Leone, Stephen R.
电子态之间的锥形交叉点通常决定了光激发分子的化学性质。最近开发的超短极紫外（XUV）脉冲源调谐到分子中的元素特定的过渡允许明确的检测电子状态切换在圆锥形的交叉点。在这里，光激发的异丙基碘和叔丁基碘分子（i-C3 H7 I和t-C4 H9 I）通过（3）Q（0）/（1）Q（1）自旋轨道状态之间的锥形交叉的碎裂是通过测量碘4d核-价跃迁的超快XUV瞬态吸收揭示的。该技术的电子状态灵敏度允许从光激发到光产物的分子解离的完整映射。在这两种分子中，在圆锥形交叉点处捕获了从（3）Q（0）态到（1）Q（1）态的低于100 fs的光激发波包转移。结果表明，如何在i-C3 H7 I和t-C4 H9 I的波包的电子状态转换的差异直接导致在两个系统的光产物分支比的差异。光激发分子的反应轨迹可能涉及通过圆锥形交叉点的过渡，这在自然界中是普遍存在的，但具有挑战性的特征。在这里，作者提供了一个完整的映射的分子解离的两个模型卤代烷的超快XUV瞬态吸收。
Conical intersections between electronic states often dictate the chemistry of photoexcited molecules. Recently developed sources of ultrashort extreme ultraviolet (XUV) pulses tuned to element-specific transitions in molecules allow for the unambiguous detection of electronic state-switching at a conical intersection. Here, the fragmentation of photoexcited iso-propyl iodide and tert-butyl iodide molecules (i-C3H7I and t-C4H9I) through a conical intersection between (3)Q(0)/(1)Q(1) spin-orbit states is revealed by ultrafast XUV transient absorption measuring iodine 4d core-to-valence transitions. The electronic state-sensitivity of the technique allows for a complete mapping of molecular dissociation from photoexcitation to photoproducts. In both molecules, the sub-100 fs transfer of a photoexcited wave packet from the (3)Q(0) state into the (1)Q(1) state at the conical intersection is captured. The results show how differences in the electronic state-switching of the wave packet in i-C3H7I and t-C4H9I directly lead to differences in the photoproduct branching ratio of the two systems. The reaction trajectories of photoexcited molecules may involve transitions through conical intersections, which are ubiquitous in nature but challenging to characterize. Here the authors provide a complete mapping of molecular dissociation of two model alkyl halides by ultrafast XUV transient absorption.