Tracing orbital images on ultrafast time scales
Tracing orbital images on ultrafast time scales
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DOI：
10.1126/science.abf3286
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发表时间：
2021-03-05
期刊：
影响因子：
56.9
通讯作者：
Hoefer，U.
中科院分区：
文献类型：
--
作者：
Wallauer，R.;Raths，M.;Hoefer，U.
前线轨道决定了基本的分子性质，如化学反应性。虽然占据轨道的电子分布可以在动量空间中通过光电发射断层成像成像，但到目前为止，还不可能通过激发或化学反应来及时跟踪分子轨道的动量-空间动力学。在这里，我们结合时间分辨光电子发射高激光谐波和动量显微镜，建立一个断层扫描，飞秒泵浦探测实验的未占用的分子轨道。我们测量了瞬态激发电子的全动量空间分布，将其激发态动力学与真实空间激发途径联系起来。因为在分子中，这种分布与轨道形状密切相关，我们的实验可能在未来提供观察超快电子在时间和空间中运动的可能性。
Frontier orbitals determine fundamental molecular properties such as chemical reactivities. Although electron distributions of occupied orbitals can be imaged in momentum space by photoemission tomography, it has so far been impossible to follow the momentum-space dynamics of a molecular orbital in time, for example, through an excitation or a chemical reaction. Here, we combined time-resolved photoemission using high laser harmonics and a momentum microscope to establish a tomographic, femtosecond pump-probe experiment of unoccupied molecular orbitals. We measured the full momentum-space distribution of transiently excited electrons, connecting their excited-state dynamics to real-space excitation pathways. Because in molecules this distribution is closely linked to orbital shapes, our experiment may, in the future, offer the possibility of observing ultrafast electron motion in time and space.