Coherent control of quantum systems with designer light fields

今天，我们对激光产生的光场在时间和空间上拥有令人难以置信的控制能力。我们可以控制激光脉冲的颜色、偏振和持续时间。我们可以组合几乎任意的频率和脉冲持续时间。我们可以控制激光束内光的空间特性。例如，我们可以创建中间有孔的光束、具有空间变化偏振矢量的光束，或者波前看起来像空间中的螺旋形的光束。 对激光场的这种程度的控制开辟了新的应用，我将探索其中的一些。虽然圆偏振激光场是手性的，但它们的波长通常比单个分子大得多，即，远离共振，分子仅经历均匀电场。我建议实现一个在空间中每个点都具有手性的激光场，这将比光电子圆二色性等常用方法更有效地区分左手和右手分子。 我将使用重合光电子光离子动量光谱（称为 COLTRIMS 或反应显微镜）来检测电离产率、光电子分子框架角分布和库仑爆炸成像中的手性相关信号。 除了开发新的结构诊断工具之外，我还建议激发水中的超快弛豫过程并对其进行成像。水二聚体是液态水最简单的近似，可以作为了解高能光子引发过程的试验场。尽管软 X 射线在不同领域都至关重要，但人们对水中的软 X 射线吸收知之甚少。了解水中 X 射线光子吸收的能量和电荷重新分布对于设计更有效的放射肿瘤学方案、解开对活体组织的遗传毒性效应的物理基础以及最大限度地减少 X 射线衍射实验期间生物样品的损伤至关重要。 这两个项目都为扩展和未来的研究提供了充足的机会。

Today we have incredible control over the optical fields created by lasers, both in time and in space. We can control the color, polarization and duration of laser pulses. We can combine nearly arbitrary frequencies and pulse durations. We can control the spatial properties of the light within the laser beam. For example we can create beams with a hole in the middle, beams with a spatially varying polarization vector, or beams whose wave front looks like a corkscrew in space. This degree of control over laser fields opens up new applications, some of which I will explore. While circularly polarized laser fields are chiral their wavelength is generally much larger than a single molecule, i.e., away from resonances a molecule experiences only a homogeneous electric field. I propose to realize a laser field that is chiral at every point in space and that will permit to distinguish left and right-handed molecules much more efficiently than commonly used methods such as photoelectron circular dichroism. I will use coincidence photoelectron photoion momentum spectroscopy, known as COLTRIMS or reaction microscopy, to detect a chirality dependent signal in ionization yields, photoelectron molecular frame angular distribution and Coulomb explosion imaging. In addition to developing a new structural diagnostic tool, I propose to excite and image ultrafast relaxation processes in water. Water dimers as the simplest approximation to liquid water can serve as testing ground to understand the processes that are initiated by high energy photons. Soft X-ray absorption in water is understood poorly despite its paramount importance in different fields. Understanding the energy and charge redistribution on X-ray photon absorption in water is vital for the design of more-efficient radiooncology schemes, for disentangling the physical basis of genotoxic effects on living tissues and for minimizing the damage of biological samples during X-ray diffraction experiments. Both projects provide ample opportunity for expansion and future research.