Tests Of Fundamental Physics Using Ramsey-Comb Spectroscopy On The Hydrogen Molecule

High-precision spectroscopy on simple systems such as atomic hydrogen has reached an unprecedented level of accuracy in recent years [1]. Experimentally determined energy levels are used to test bound-state quantum electrodynamics (QED). However, theoretical values for the energy levels were limited by the uncertainty of experimentally determined parameters such as the proton charge radius (r _p ). In 2010, the CREMA collaboration performed a spectroscopic measurement on muonic hydrogen. From this, r _p was extracted with a ten times higher accuracy but also showed a 5σ discrepancy to the CODATA-2010 value [2]. This so-called proton radius puzzle remains unsolved. A possible solution to this problem can be obtained from measurements in other systems.