A D V A N C E D M A T E R I A L S & P R O C E S S E S | J U L Y / A U G U S T 2 0 2 2 1 1 binding mechanism forming a molecule between a tiny, charged particle and a gigantic Rydberg atom. The molecule exhibits a special feature—it consists of a positively charged ion and a neutral atom in a so-called Rydberg state. These Rydberg atoms have grown in size a thousand times compared to typical atoms. As the charge of the ion deforms the Rydberg atom in a very specific way, the bond between the two particles emerges. To verify and study the molecule, the researchers prepared an ultra-cold rubidium cloud, which was cooled down close to absolute zero at -273°C. In these ultra-cold atomic ensembles, the ionization of single atoms with laser fields prepares the first building block of the molecule—the ion. Additional laser beams excite a second atom into the Rydberg state. The electric field of the ion deforms this gigantic atom. Notably, the deformation can be attractive or repulsive depending on the distance between the two particles, letting the binding partners oscillate around an equilibrium distance and inducing the molecular bond. The distance between the binding partners is unusually large and amounts to about a tenth of the thickness of a human hair. An open vacuum chamber with the electric field control and the first lens of the ion microscope sitting in the center. Courtesy of Nicolas Zuber. A special ion microscope made this observation possible. It was developed, built, and commissioned by the researchers at the 5th Physical Institute in close collaboration with the workshops of the University of Stuttgart. In contrast to typical devices working with light, the researcher’s special ion microscope influences the dynamics of charged particles with the help of electrical fields to magnify and image the particles onto a detector. Next, the researchers aim to study dynamical processes within this unusual molecule. www.pi5.uni-stuttgart.de.
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