Ion microscope

Spatially Resolved Ultracold Rydberg Physics

5th Institute of Physics

This project aims at spatially resolved studies of heteronuclear Rydberg quantum gases by combining ultracold samples of rubidium and lithium with ion microscopy techniques.

The Project

This project aims at the spatially resolved investigation of ultracold Rydberg physics. To this end, our experimental apparatus is designed to combine the ability of producing ultracold quantum gases of rubidium and lithium with the controlled creation of individual Rydberg atoms. An ion microscope allows for the spatial resolution of the Rydberg atoms. Research goals are the investigation of strongly-interacting quantum matter and the creation of (heteronuclear) Rydberg molecules either as a microscopic correlation probe for degenerate quantum gases or as a novel tool to study ultracold ion-atom scattering.

Atom ion scattering
Figure 1: Temporal evolution of the lithium-6 ion-atom scattered wave packet for a scattering length of +R* (R* being the characteristic radius of the ion-atom interaction). The unfilled curve is the initial Rydberg molecule wave function. The scattered wave packet is shown in steps of 50ns from top to bottom. It splits into a free, expanding and a bound shell, indicating molecular ion formation. The inset demonstrates the S-wave character of the scattered wave packet.

Recently, we have proposed a novel experimental method to extend the investigation of ion-atom collisions from the so far studied cold regime to the unexplored ultracold regime. The key aspect of this method is the use of a Rydberg molecule to initialize the ultracold ion-atom scattering event. Together with M. Tomza and M. Tarana, we conducted simulations for the lithium ion-atom system which show how the initial Rydberg molecule wave function, freed by photoionization, evolves in the presence of the ion-atom scattering potential (see figure 1). We predict that the scattering length can be experimentally determined either from the velocity of the scattered wave packet or from the molecular ion fraction.

Ion microscope
Figure 2: Detail of our setup showing part of the two-species Zeeman slower, the MOT and the science chamber, the translation stage for the optical transport, and the chimney housing the ion microscope with the delay line detector at the very top.

Our setup

Our experimental apparatus (see figure 2) is designed to produce ultracold quantum gases of rubidium and lithium. Starting with hot atomic beams from two ovens, the first slowing step is provided by a two-species Zeeman slower. Next, further cooling is achieved by a MOT which is followed by an optical transport of the cold atomic clouds to the science chamber where evaporation cooling in an optical dipole trap will finally yield ultracold trapped dilute atomic clouds.

An in-vacuum asphere and an electric field control (see icon) inside the science chamber will allow for the creation and control of single Rydberg atoms.

To efficiently detect the single Rydberg atoms, we will employ either electric field or photoionization. A Rydberg ion imaging system, consisting of an ion microscope (see icon) and a delay-line detector, will finally allow to record the Rydberg ions with temporal and spatial resolution.

Vacuum chamber of the Rb-Li experiment
Figure 3: A view into our lab and the central part of our setup showing the vacuum chamber hosting our quantum gas and the first lens of the ion microscope.

Project Publications

  1. 2023

    1. Y.-Q. Zou, M. Berngruber, V. S. V. Anasuri, N. Zuber, F. Meinert, R. Löw, T. Pfau, Observation of Vibrational Dynamics of Orientated Rydberg-Atom-Ion Molecules, Phys. Rev. Lett. 130, 023002 (2023).
  2. 2022

    1. S. Tiwari, F. Engel, M. Wagner, R. Schmidt, F. Meinert, S. Wüster, Dynamics of atoms within atoms, New Journal of Physics 24, 073005 (2022).
    2. N. Zuber, V. S. V. Anasuri, M. Berngruber, Y.-Q. Zou, F. Meinert, R. Löw, T. Pfau, Observation of a molecular bond between ions and Rydberg atoms, Nature 605, 453--456 (2022).
  3. 2021

    1. C. Veit, N. Zuber, O. A. Herrera-Sancho, V. S. V. Anasuri, T. Schmid, F. Meinert, R. Löw, T. Pfau, Pulsed Ion Microscope to Probe Quantum Gases, Phys. Rev. X 11, 011036 (2021).
  4. 2020

    1. R. Mukherjee, F. Sauvage, H. Xie, R. Loew, F. Mintert, Preparation of ordered states in ultra-cold gases using Bayesian optimization, New Journal of Physics 22, 075001 (2020).
  5. 2018

    1. T. Schmid, C. Veit, N. Zuber, R. Löw, T. Pfau, M. Tarana, M. Tomza, Rydberg Molecules for Ion-Atom Scattering in the Ultracold Regime, Phys. Rev. Lett. 120, 153401 (2018).

We are looking for motivated new team members!

We currently offer a Ph.D. position on our ion microscope project which aims at the spatially resolved investigation of ultracold Rydberg physics. If you are interested in the project, don’t hesitate to visit us in the lab (4.136) or contact us:

R. Löw, T. Pfau

Project Team


This image shows Tilman Pfau

Tilman Pfau

Prof. Dr.

Head of Institute

This image shows Robert Löw

Robert Löw


Deputy Director

This image shows Florian Meinert

Florian Meinert


Group Leader

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