"Attoclock-Rabbitt" - Bicircular laser fields as tool for molecular ionization time measurements

“Attoclock-Rabbitt”——双圆激光场作为分子电离时间测量的工具

• 批准号: 411646277
• 负责人: Professor Dr. Reinhard Dörner
• 金额: --
• 依托单位: Institut für Kernphysik
• 依托单位国家: 德国
• 项目类别: Priority Programmes
• 财政年份: 2018
• 资助国家: 德国
• 起止时间: 2017-12-31 至 2023-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/411646277?language=en
• 关键词: Attoclock; Rabbitt; Bicircular; laser; fields

This project aims to exploit tailored light fields as a tool to answer a seemingly simple question: Does the emission time of a photoelectron ejected from a molecule by multiphoton absorption depend on its emission direction? To give an example: we ask whether the ejection of an electron from CO takes longer in case of emission towards the C or towards the O side of the molecule. The expected time differences are in the attosecond regime. Quantum mechanically time-differences are encoded in phase-differences, thus our question translates to determining the phase of the electron wave packet as function of angle to the molecular axis. To measure this phase, we suggest a new scheme termed “Attoclock-RABBITT”. Within this scheme, we combine the measurement of an ionization instant (in a manner similar to the established RABBITT technique) with a COLTRIMS Reaction Microscope, which gives access to the molecular frame of reference by detection the molecular ion fragments.The employed laser field will consist of a strong circularly polarized 400 nm field mixed with a weak circular 800nm co-rotating dressing field. As we have learned in the previous QUTIF funding period, this bicircular field combination maps the relative phase between the two colors to an electron emission angle in the laboratory frame. Sidebands in the electron ATI spectrum show the known RABBITT intensity oscillations as function of that angle and from these oscillations, one can deduce the emission times. In our suggested approach, the emitted electrons are measured in coincidence with ionic fragments of the molecule using a COLTRIMS Reaction Microscope. From the emission direction of the ionic fragments we are able to deduce the molecular orientation. This way we obtain the “Attoclock-RABBITT” traces, i.e. ionization times, in the molecular frame. As this is a novel scheme, we suggest to first benchmarking it on atomic hydrogen. We will then use it to study the following predicted effects: Using Ne2 we will search for the predicted divergence of the ionization time at a Cohen/Fano-interference. Employing H2 we will provide benchmark data on the only molecule for which quasi-exact theoretical treatment is possible today. In experiments on CO we will search for the predicted asymmetries of the emission time to the two sides and, aim to visualize a shape resonance in the time domain. Finally, for CF4 we will test if the technique can be applied to more complex molecules. The project is at the heart of QUTIF as the types of tailored field have been explored in several previous QUTIF projects. The first funding period has led to widespread theoretical experience in handling these fields. Also experimentally, the optical tools for this project have been developed. Without this extensive experience from QUTIF it would not have been possible to now aim for the next step of application of tailored fields.

该项目旨在利用定制的光场作为工具来回答一个看似简单的问题：通过多光子吸收从分子中射出的光电子的发射时间是否取决于其发射方向？举个例子：我们要问，在向分子的C侧或O侧发射的情况下，从CO发射电子是否需要更长的时间。预期的时间差在阿秒范围内。量子力学的时间差被编码在相位差中，因此我们的问题转化为确定电子波包的相位作为与分子轴的角度的函数。为了测量这个相位，我们提出了一个新的方案，称为“Attoclock-RABBITT”。在这个方案中，我们结合联合收割机的电离瞬间的测量（以类似于建立的RABBITT技术的方式）与COLTRIMS反应显微镜，它提供了通过检测分子离子碎片访问的分子参考框架。正如我们在之前的QUTIF资助期间所了解到的那样，这种双环场组合将两种颜色之间的相对相位映射到实验室框架中的电子发射角。电子ATI谱中的边带显示了已知的RABBITT强度振荡作为该角度的函数，并且从这些振荡可以推导出发射时间。在我们建议的方法中，发射的电子与使用COLTRIMS反应显微镜的分子的离子片段重合测量。从离子碎片的发射方向，我们能够推断出分子取向。通过这种方式，我们获得了“Attoclock-Rabbitt”迹线，即分子框架中的电离时间。由于这是一个新的方案，我们建议首先将其基准原子氢。然后，我们将使用它来研究以下预测的影响：使用Ne 2，我们将搜索科恩/范诺干涉下电离时间的预测发散。采用H2，我们将提供基准数据的唯一分子，准精确的理论治疗是可能的今天。在CO的实验中，我们将寻找预测的发射时间的不对称性的两侧，并旨在可视化的形状共振在时域。最后，对于CF 4，我们将测试该技术是否可以应用于更复杂的分子。该项目是QUTIF的核心，因为定制字段的类型已经在之前的几个QUTIF项目中进行了探索。第一个供资期在处理这些领域方面产生了广泛的理论经验。此外，实验，该项目的光学工具已经开发。如果没有QUTIF的丰富经验，我们现在就不可能瞄准定制领域应用的下一步。