"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喷射出的光电子的发射时间是否取决于其发射方向？如果电子从 CO 发射到分子的 C 侧或 O 侧，则需要更长的时间。预期的时间差处于阿秒范围内，量子机械时间差被编码为相位差。转化为确定电子波包的相位作为与分子轴的角度的函数。为了测量该相位，我们提出了一种称为“Attoclock-RABBITT”的新方案，在该方案中，我们结合了电离瞬间的测量。与已建立的 RABBITT 技术类似的方式）使用 COLTRIMS 反应显微镜，通过检测分子离子碎片来访问分子参考系。所采用的激光场将由强圆偏振 400 nm 组成正如我们在之前的 QUTIF 资助期间了解到的那样，这种双圆形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 谱显示了已知的 RABBITT 强度振荡作为该角度的函数，并且根据这些振荡，可以推断出发射时间。在我们建议的方法中，发射的电子是与离子一致测量的。使用 COLTRIMS 反应显微镜从离子碎片的发射方向我们能够推断出分子方向，这样我们就可以获得分子框架中的“Attoclock-RABBITT”痕迹，即电离时间。是一个新颖的方案，我们建议首先对原子氢进行基准测试，然后我们将使用它来研究以下预测效果：使用 Ne2，我们将搜索电离时间的预测发散。利用 H2，我们将提供目前唯一可以进行准精确理论处理的分子的基准数据，在 CO 实验中，我们将寻找两侧发射时间的预测不对称性，最后，对于 CF4，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，因为在之前的几个 QUTIF 中已经探索了定制场的类型。第一个资助期带来了处理这些领域的广泛理论经验，如果没有 QUTIF 的丰富经验，现在就不可能开发出用于该项目的光学工具。定制领域的应用。