Stimulated Raman spectroscopy of H2 with absolute frequency calibration

H2 is the simplest neutral molecule in the universe and it is a benchmark system for testing quantum electrodynamics and physics beyond the standard model via highly accurate measurements of its transition frequencies [1-3]. However, the retrieval of unperturbed transition frequencies is hampered by the weakness of quadrupole transition moments, which determines poor signal-to-noise ratios at low pressure. Alternatively, it is possible to precisely model the H2 lineshapes at higher pressure in order to account for the strong collisional effects that distort the absorption profile and eventually extrapolate by proper fitting an accurate line centre.