Efficient and robust coherent electronic excitation in molecules with temporally shaped femtosecond laser pulses

利用时间成形的飞秒激光脉冲对分子进行高效、鲁棒的相干电子激发

• 批准号: 277176996
• 负责人: Professor Dr. Thomas Baumert
• 金额: --
• 依托单位: Experimentalphysik III: Femtosekundenspektroskopie und ultraschnelle Laserkontrolle
• 依托单位国家: 德国
• 项目类别: Research Grants
• 财政年份: 2015
• 资助国家: 德国
• 起止时间: 2014-12-31 至 2017-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/277176996?language=en
• 关键词: Efficient; robust; coherent; electronic; excitation

Coherent electronic excitation in atoms with the help of laser light forms the basis of many quantum technologies. Adiabatic processes are of particular interest, as they allow for efficient population transfer (up to 100%) and in addition show robustness with respect to variations of experimental parameters as for example intensity fluctuations. Rapid Adiabatic Passage (RAP) is a prime example to that end. Nuclear motion in molecules hampers such excitation processes significantly. Therefore adiabatic excitation in molecules is neither theoretically nor experimentally thoroughly explored. More than a decade ago theory proposed excitation with ultra broadband short laser pulses being stretched via a linear frequency sweep into the picosecond regime. In this limit the excitation is similar to the atomic RAP case, experimental realizations were not reported. We now suggest to adapt the electric field of a laser well directed to the coupled electron nuclear dynamics via specific frequency sweeps and temporal intensity envelopes in order to demonstrate robust population transfer in a molecule. Simulations on a simple harmonic oscillator model reveal efficient and robust new excitation schemes. Taking the potassium dimer as a prototype, this project aims at experimental demonstrations of these excitation schemes. Specifically shaped laser pulses are used for excitation and the final population in the neutral manifold is probed via photoelectron spectroscopy with the help of a temporally delayed laser pulse. It is beneficial to use the potassium dimer as a prototype as quantum mechanical simulations can be performed with high accuracy on this molecule. The joint expertise of the Baumert group (Uni Kassel; experiment) and Wollenhaupt group (Uni Oldenburg; quantum mechanical simulations) is brought together in order to explore the limits of such an approach by a direct comparison of experiments on this molecule to simulations.

在激光的帮助下，原子中的相干电子激发形成了许多量子技术的基础。绝热过程特别令人感兴趣，因为它们允许有效的种群转移（高达100%），而且对实验参数的变化（例如强度波动）表现出鲁棒性。快速绝热通道（RAP）就是一个很好的例子。分子中的核运动明显阻碍了这种激发过程。因此，分子中的绝热激发在理论上和实验上都没有得到充分的探讨。十多年前，理论提出了通过线性频率扫描将超宽带短激光脉冲拉伸到皮秒范围的激励方法。在此极限下激发与原子RAP类似，实验实现未见报道。我们现在建议通过特定的频率扫描和时间强度包络使激光的电场适应于耦合的电子核动力学，以证明分子中强大的种群转移。在简单谐振子模型上的仿真显示了新的激励方案的有效性和鲁棒性。本项目以二聚体钾为原型，对这些激励方案进行实验论证。特定形状的激光脉冲被用于激发，中性流形中的最终种群通过光电子能谱在时间延迟激光脉冲的帮助下探测。利用二聚体钾作为原型，可以对该分子进行高精度的量子力学模拟。Baumert小组（Uni Kassel；实验）和Wollenhaupt小组（Uni Oldenburg；量子力学模拟）的联合专业知识被汇集在一起，以便通过对该分子的实验与模拟的直接比较来探索这种方法的局限性。