Stimulated Raman scattering metrology of molecular hydrogen

Abstract Frequency combs have revolutionized optical frequency metrology, allowing one to determine highly accurate transition frequencies of a wealth molecular species. These progresses only marginally benefited infrared-inactive transitions, due their inherently weak cross-sections. Here we overcome this limitation by introducing stimulated-Raman-scattering where comb is exploited calibrate the detuning between pump and Stokes excitation lasers. We apply approach investigation hydrogen, which recognized benchmark for tests quantum electrodynamics theories that describe physics beyond standard model. Specifically, measure Q(1) fundamental line H 2 around 4155 cm −1 with few parts-per-billion uncertainty, comparable theoretical ab initio calculations more than decade better experimental state art. Our comb-calibrated stimulated Raman scattering spectrometer extends toolkit metrology as it can be applied, simple technical changes, many other over 50-5000 range covers also purely rotational bands.