Wallauer R, Raths M, Stallberg K, Münster L, Brandstetter D, Yang X, Güdde J, Puschnig P, Soubatch S, Kumpf C, Bocquet F C, Tautz F S, Höfer U
Fachbereich Physik und Zentrum für Materialwissenschaften, Philipps-Universität Marburg, Renthof 5, 35032 Marburg, Germany.
Peter Grünberg Institut (PGI-3), Forschungszentrum Jülich, 52425 Jülich, Germany.
Science. 2021 Mar 5;371(6533):1056-1059. doi: 10.1126/science.abf3286. Epub 2021 Feb 18.
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.
前沿轨道决定了诸如化学反应性等基本分子性质。尽管占据轨道的电子分布可以通过光发射断层扫描在动量空间中成像，但迄今为止，还无法及时跟踪分子轨道在动量空间中的动力学过程，例如通过激发或化学反应来实现。在这里，我们将使用高次激光谐波的时间分辨光发射与动量显微镜相结合，建立了一个未占据分子轨道的断层扫描飞秒泵浦-探测实验。我们测量了瞬态激发电子的完整动量空间分布，将它们的激发态动力学与实空间激发路径联系起来。由于在分子中这种分布与轨道形状密切相关，我们的实验未来可能提供在时间和空间上观测超快电子运动的可能性。
