Imaging single Rydberg electrons and ions in a quantum gas

• Applicant: Professor Dr. Tilman Pfau
• Subject Area: Optics, Quantum Optics and Physics of Atoms, Molecules and Plasmas
• Term: from 2014 to 2022
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 262764871

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.

• DFG Programme: Reinhart Koselleck Projects