Time-resolved low energy electron diffraction from large excited molecules on surfaces

为了在分子水平上观察过程，有必要开发一种在微观尺度上结合时间和空间领域的技术。在表面化学的情况下，测定结构的标准工具是低能电子衍射（LEED）。对于时间分辨的LEED实验，我们将开发一种电子枪，它可以产生超短和相干的电子脉冲，预期时间分辨小于5皮秒。在这种时间分辨率下，我们可以通过泵浦和探针实验来研究大型吸附分子的低频模式，例如C60在Ag（100）上的受挫平移。该实验将作为时间分辨LEED的原理证明。解释随时间变化的实验LEED数据需要一种改进的LEED计算方法。从这些实验结合提升LEED数据评估，我们想要确定C60的一次激发低频模式如何随时间衰减（和衰减）（在皮秒尺度上）。这些数据可以提供有关C60分子与底层底物和邻近C60分子耦合的有用信息。

In order to watch processes on the molecular level, it is necessary to develop a technique that combines the time and space domain on a microscopic scale. For the case of surface chemistry the standard tool for structure determination is low energy electron diffraction (LEED). For time-resolved LEED experiments we shall develop an electron gun that produces ultra short and coherent electron pulses with an expected time resolution of less than 5 picoseconds. With this time-resolution we are able to study low-frequency modes of large adsorbed molecules such as the frustrated translation of C60 on Ag(100) by a pump & probe experiment. This experiment will serve as proof of principle for time-resolved LEED. The interpretation of the time dependent experimental LEED data requires an improved approach for the LEED calculations. From these experiments in combination with the elevated LEED data evaluation we want to determine how the once excited low-frequency mode of C60 damps (and dephases) with time (on the picosecond scale). These data may provide useful information about the coupling of the C60 molecule with the underlying substrate and neighbouring C60 molecules.