Bonn 2025 – scientific programme
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MO: Fachverband Molekülphysik
MO 3: Rydberg Atoms, Ions, and Molecules (joint session Q/MO)
MO 3.4: Talk
Monday, March 10, 2025, 11:45–12:00, HS I
Electronically Excited Cold Rydberg Ion Crystals — •Marion Mallweger1, Natalia Kuk1, Harry Parke1, Ivo Straka1, Robin Thomm1, Vinay Shankar1, Weibin Li3, Igor Lesanovsky2,3, and Markus Hennrich1 — 1Stockholm University, Stockholm, Sweden — 2Institut für Theoretische Physik, Universität Tübingen, Germany — 3School of Physics and Astronomy, University of Nottingham, United Kingdom
Trapped Rydberg ions harness two advantages: a well defined confinement through the charge of the ion and strong interactions through its large principle quantum number. In the experiments presented here a trapped strontium ion was excited from the metastable 4D to Rydberg states. While for the ground state of the ion, the polarizability is negligible, for Rydberg ions it increases as ∼ n7. Thus, the high polarizability of the Rydberg state with respect to the ground state leads to a change in radial confinement during the Rydberg excitation. For an ion crystal, this change can be enough to cause a structural phase transition from a linear configuration in the lower-lying electronic states to a zigzag configuration in the Rydberg state. We explore and characterize this electronic state dependent structural phase transition. We investigate this effect via spectroscopy scans of the Rydberg resonance with varying radial confinement close to the transition point of the zigzag crystal configuration. By tuning the polarizability, the change in radial trap confinement and therefore the transition point can be tuned. This enables a novel method for studying molecular phenomena with ions in the well-isolated environment of a Paul trap.
Keywords: Trapped ions; Rydberg