Spectroscopy of molecular Hydrogen Ions for the Metrology of fundAmEntal constants and mass RAtios (SHIMAERA)

Precision spectroscopy is a rapidly advancing field, where advanced experimental and theoretical methods converge to measure fundamental constants and test the laws of nature with remarkable accuracy. In this MSCA project, I propose innovative laser spectroscopy experiments in molecular hydrogen ions (MHI) to improve the determination of the proton-to-electron mass ratio, a very important fundamental constant of nature. My current group at LaserLaB Amsterdam and the host research group at the Kastler Brossel Laboratory (LKB) in Paris are both key players in the field. The MHI spectroscopy experiments performed in Amsterdam, combined with the quantum electrodynamics (QED) calculation methods developed at LKB, have enabled an improved determination of the proton-to-electron mass ratio and the electron relative atomic mass. Thanks to these exceptional results, as of 2022 MHI spectroscopy contributes to the definition of the CODATA internationally recommended values of the fundamental physics constants. To improve this further, I will implement Doppler-free laser excitation of an MHI quadrupole and/or two-photon vibrational transition, perform precision laser spectroscopy of the excited transition, and extract an even improved determination of the proton-to-electron mass ratio by comparing the measured transition frequency to the theoretically predicted value. This MSCA fellowship will give me the opportunity to do outstanding research by combining my hands-on expertise in precision spectroscopy with the expertise of the host research group in frequency metrology and QED calculations. It will also give me the perfect platform to foster international collaborations within my personal scientific network and to lay out my longer-term research plans, including developing the first MHI-based optical molecular clock to advance novel applications across science and industry.