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

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%），并且还对实验参数的变化（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。分子中的核运动显著地阻碍了这种激发过程。因此，分子中的绝热激发既没有在理论上也没有在实验上进行彻底的探索。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发。在这个极限下，激发类似于原子RAP的情况，实验实现没有报道。我们现在建议通过特定的频率扫描和时间强度包络来调整激光的电场，使其与耦合电子核动力学方向一致，以证明分子中的强布居转移。在简谐振子模型上的模拟揭示了高效和鲁棒的新激励方案。本计画以钾二聚体为原型，对这些激发机制进行实验验证。特定形状的激光脉冲用于激发和中性歧管中的最终人口通过光电子能谱探测的帮助下，时间延迟的激光脉冲。使用钾二聚体作为原型是有益的，因为可以对该分子进行高精度的量子力学模拟。Baumert小组（Uni卡塞尔;实验）和Wollenhaupt小组（Uni Oldenburg;量子力学模拟）的联合专业知识汇集在一起，以探索这种方法的限制，通过直接比较这种分子的实验模拟。

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.