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Chemical Physics and Spectroscopy

The Willitsch Group - Cold and Controlled Molecules and Ions

Five bright blue glowing dots are arranged in a horizontal line against a dark blue background. Below them, text reads: A string of laser-cooled calcium ions.

A blue background with several red and blue spheres containing molecular structures. Small blue spheres are shown moving between two blue spheres. The text at the bottom reads: "Conformationally controlled chemical reactions".

A complex scientific apparatus with many metallic parts, wires, and a green light in the center. The text "Molecular quantum technologies experiment" is at the bottom.

An illustration of a blue, oval-shaped object with yellow dots and brown protrusions, surrounded by a bright yellow glow and red light beams. The text below reads: "Cold ions immersed in a cloud of ultracold atoms".

A close-up of a scientific instrument with two long, shiny metal rods, each with a textured surface, extending from a circular metal plate. The rods are supported by white ceramic insulators. The text at the bottom reads: "A Stark decelerator for generating cold molecules".

Welcome to the Cold and Controlled Molecules and Ions group at the University of Basel led by Prof. Stefan Willitsch and the astrochemistry subgroup led by Dr Jutta Toscano. Our research is concerned with the preparation and control of cold molecules and molecular ions and their applications in both chemistry and physics. On this website, you can find information about our group, our research, our teaching and opportunities to join us.

Recent News

A red laser beam and a yellow wavy line pass through two small blue spheres and one large purple sphere.

In our recent publication in Nature Communications, we report the identification and coherent control of “forbidden” vibrational transitions in single trapped nitrogen molecular ions without destroying them. This work opens up new possibilities for highly precise molecular clocks, quantum bits, and tests of fundamental laws of physics.
Read more:
Research article in Nature Communications
University of Basel news article

We are delighted to warmly welcome Christian Schaub from TU Darmstadt, Germany. He is now now working on the optical clock project.

We are delighted to warmly welcome Dr. Corentin Rossi from Université Paris-Saclay. He is now working on the COCO CMB project.

Research

Learn about our research topics

Teaching

Course materials for HS26 on ADAM:
Physikalische Chemie II - Teil 2: Quantentheorie (HS 26)

Open positions

PhD position: Development of a single-ion optical clock within the new National Competence Center for Research “Precision”
More information

Our group

Meet our group

Recent publications

A. Shlykov, M.L. Diouf, R. Karl, M. Roguski, U.C. Joshi and S. Willitsch,
“Quantum-logic spectroscopy of forbidden vibrational transitions in single nitrogen molecular ions”
Nature Communications (2026) (arxiv.org/abs/2603.10553) (supporting data at https://zenodo.org/records/18935655)

N. S. Kumar, P. Paliwal, M. Popov, X. Li, A. Li, H. Guo and S. Willitsch,
“Single-molecule cold chemistry: Isotopic branching ratios of the H₂O⁺ + HD reaction at cryogenic temperatures”
(arXiv:2610.32904)

C. Yin, S. Willitsch and M. Meuwly,
“Full-Dimensional Reactive Potential Energy Surfaces for OCS⁺ → CO+S⁺ Dissociation: Ground and Excited States”
J. Phys. Chem. A (2026) 130 (40): 7887–7895. (arXiv:2605.14617)

C. He, X. Zhang, C. Yin, M. Meuwly and S. Willitsch,
“Charge-partition pathways in strong-field photoionization of carbonyl sulfide monomers and dimers”
Phys. Chem. Chem. Phys. (2026) 28 (36): 22557–22566. (arXiv:2607.08167)

A. Poindron and S. Willitsch,
“Anharmonic motion of a trapped ion under the influence of different drives in an ion-nanomechanical hybrid system”
Phys. Rev. Research 8, 033028 (2026)

More publications