Imaging single Rydberg electrons and ions in a quantum gas

电子轨道是我们理解化学、分子和固态物理的基本组成部分。虽然在许多情况下，它们可以计算，并在几乎任何物理或化学教科书中以图形方式可视化，但它们没有在真实的空间中直接光学成像。奇异的轨道，如所谓的一维原子或圆形状态，已经被创造出来，并间接证明存在。在受驱动的电子系统中，例如在光吸收或能量传输现象中的动态轨道变化在理论上是很好理解的，但也从未被直接成像。我们提出了一种新的直接空间成像方法的静态和动态变化的轨道的一个单一的电子，这也可以扩展到离子。其基础是单个电子与玻色-爱因斯坦凝聚体（BEC）中的可极化原子的相互作用，BEC充当造影剂，导致可测量的密度变化，其可以通过例如暗场显微镜直接成像。为此，轨道的大小必须大于光学分辨率，这可以通过激发里德堡电子到~100以上的主量子数来实现。此外，对于离子，相互作用的范围在光学分辨率极限的量级上，使得相应的原位成像能力也将允许对量子气体中的单个离子周围的预期极化子进行成像。单个超冷离子最终能否在量子气体中被捕获并成像，是该研究项目的一个具有挑战性的观点。

Electron orbitals are a fundamental building block in our understanding of chemistry, molecular and solid state physics. Although in many cases they can be calculated and are visualized graphically in virtually any physics or chemistry textbook they have not been directly optically imaged in real space. Exotic orbitals like so called one dimensional atoms or circular states have been created and indirectly proven to exist. Dynamical orbital changes in driven electronic systems e.g. in light absorption or energy transport phenomena are theoretically well understood, but also have never been directly imaged. We propose a novel direct spatial imaging method for static and dynamical changes of the orbital of a single electron, which can also be extended to ions. The basis is the interaction of a single electron with the polarisable atoms in a Bose-Einstein Condensate (BEC), which acts as a contrast agent, resulting in measurable density change which can be imaged directly by e.g. dark field microscopy. For this the size of the orbitals must be larger than the optical resolution, which can be achieved by exciting Rydberg electrons to principle quantum numbers above ~100. Also for ions the range of interaction is on the order of the optical resolution limit such that the respective in situ imaging capabilities would also allow to image the expected polarons around a single ion in a quantum gas. Whether a single ultracold ion can ultimately be trapped and imaged in a quantum gas is a challenging perspective of the research project.