Stimulated Raman Spectroscopy of H2 with Absolute Frequency Calibration

H
₂
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 H
₂
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.