Observation and measurement of molecular flow using stimulated Raman gain spectroscopy

We report the observation and measurement of frequency shifts in stimulated Raman gain spectroscopy (SRGS) resulting from subsonic molecular nitrogen flows emerging from a simple nozzle. The flow velocity in the region of the measurement was determined to be 145 m/s with an accuracy of ±30 m/s. It is expected that significantly better flow-velocity resolution will be obtained in future experiments using inverse Raman scattering.