SAMOP 2021 – scientific program
PV IX: Plenary Talk
Friday, September 24, 2021, 09:45–10:30, Audimax
Precision metrology of molecular hydrogen for tests of fundamental physics — •Wim Ubachs — Department of Physics and Astronomy, VU University Amsterdam, Netherlands
The hydrogen molecule is the smallest neutral chemical entity and a benchmark system of molecular spectroscopy. The comparison between highly accurate measurements of transition frequencies and level energies with quantum calculations including all known phenomena (relativistic, vacuum polarization and self-energy) provides a tool to search for physical phenomena in the realm of the unknown: are there forces beyond the three included in the Standard Model of physics plus gravity, are there extra dimensions beyond the 3+1 describing space time ? Comparison of laboratory wavelengths of transitions in hydrogen may be compared with the lines observed during the epoch of the early Universe to verify whether fundamental constants of Nature have varied over cosmological time. A variety of results are obtained: (1) Dissociation limits of H2 and D2 are measured to 10-digit accuracy; (2) Measurement of H2 shape resonances lead to an accurate determination of the scattering length of H + H collisions; (3) Measurements are being extended to radioactive tritium species; (4) Measurement of a vibrational splitting in the HD+ molecular ion yield the most accurate value for the proton-electron mass ratio.