Precision spectroscopy

The main research direction of our group is the use of ultra-precise laser measurements to test quantum physics. We do this at different levels using different experimental approaches. One example is searching for variability in fundamental constants with optical atomic clocks. We developed a new experimental approach to search for short-time variations in the fine-structure constant [18] and used it to constrain models of topological dark matter [18].

This led us to perform the first such measurement using a global network of optical atomic clocks [26]. Another example is testing the quantum-electrodynamics (QED) sector of the standard model for molecular systems. We focus on molecular hydrogen [25], the simplest molecule in nature and therefore calculable from first principles of quantum theory at a high level of accuracy.

We developed a cavity-enhanced spectrometer based on an optical resonator with exceptionally high finesse (F = 637000) [43]. The accuracy reached with this instrument corresponds to testing QED at the fifth significant digit. More recently, we moved this cavity-enhanced technology to a deep cryogenic regime [59, 80], improving the accuracy by over an order of magnitude [80]. In 2023, we launched a project aimed at trapping cold molecular hydrogen.

We develop an ultra-strong optical-dipole trap and a novel cryogenic molecular source which, combined, will allow us to confine H₂ molecules with the ultimate goal of improving the accuracy of H₂ energy-structure measurements by orders of magnitude.

We also perform accurate studies of atomic and molecular interactions and collisional phenomena through precision spectroscopy of collision-induced molecular line shapes. This allows us to validate quantum-chemical calculations of intermolecular potential energy surfaces [36, 38, 50], test quantum-scattering calculations [50, 67] and test line-shape models describing collisional relaxation and velocity changes [5, 34, 60].