Abstract：

　　Modern laser spectroscopic and metrology methods, involving atomic clocks and frequency comb lasers, allow for ever more refined and accurate determination of the quantum level structure of the smallest molecules, the hydrogen molecule, the hydrogen molecular ion, and its isotopologues. At the same time advanced quantum calculations, including non-adiabatic, relativistic and QED-effects on these small systems have become possible at a high level of accuracy. A comparison between experiment and theory for the benchmark dissociation energy reveals that both are in agreement at the sub-MHz level. This result can be interpreted as a test of QED in molecules, but also constraints on possible 5th forces or higher dimensions can be deduced. The abundancy and observation of H2 in quasar radiation can be used for deducing possible variations of the proton-electron mass ratio, a phenomenon that surpasses known physics. Currently the focus of research is shifting to the measurement of vibrational transitions in hydrogen; in view of the long lifetimes of those quantum states, that opens up a new avenue for precision metrology on molecules and the search for new physics.

Biosketch：

　　Wim Ubachs got his PhD degree in 1986 in Nijmegen University on “High resolution spectroscopy on diatomic hydrides”. Since 1988 he affiliated with Vrije Universiteit Amsterdam, as Lecturer, Senior Lecturer and Full professor. From 2000-2010 he became the director of the Laser Centre at VUA, and 2010-2014 the head of the Physics Department. At VUA he was involved in different aspect of laser spectroscopy, building narrowband lasers for XUV spectroscopy, harmonic generation and frequency comb lasers, studying perturbations in molecular spectra, spectroscopy for atmospheric and astrophysics, but mostly working on the hydrogen molecule.