Improved Determination of Fundamental Constants and Test of Fundamental Physics with Doppler-Free THz Spectroscopy of HD+

The understanding of the quantum nature of atoms and molecules may be tested by comparing accurate theoretical ab-initio predictions with the results of precision spectroscopy experiments. A comparison based on the molecular hydrogen ions, the simplest three-body molecular systems, may be exploited also to determine the values of a set of fundamental constants and to search for any deviation of the nucleus-nucleus interaction from the Coulomb force. Achieving improvements in these results compared to the state-of-the-art is a challenging task on both experimental and theoretical sides.