Measurements of a supersonic velocity in a nitrogen flow using inverse Raman spectroscopy

Results of supersonic molecular flow-velocity measurements using inverse Raman spectroscopy are reported for the first time to our knowledge. Because of potential wind-tunnel applications, flowing N(2) molecules are probed directly, and their flow velocity, temperature, and density are measured. The uncertainties are less than 5% for the velocity measurements and about 10% for the temperature and density measurements. To achieve the quoted precision, I(2) fluorescence, I(2) saturated-absorption, and differential-detection techniques are used to stabilize the probe laser, provide an absolute-frequency reference, and reduce detection noise, respectively.