Coherent anti-Stokes Raman scattering is demonstrated as a quantitative diagnostic in low-density flows by mapping H2 velocity and translational temperature inside and outside the nozzle of a resistojet. A spatial resolution of better than 35 µm along the flow direction and 350 µm transverse to it was attained in a density as low as 5 × 1015 cm-3. The accuracy of the velocity, inferred from the Doppler shift of the Q(1) Raman resonance, was limited by the scan linearity of the laser to ±0.2 km/s. Translational temperatures, inferred from linewidths and complicated by saturation and ac Stark effects, had an accuracy of ∼20%. A discussion of applicability to molecular nitrogen is presented.
© 1997 Optical Society of America
Original Manuscript: April 19, 1996
Revised Manuscript: October 11, 1996
Published: May 20, 1997
Edward J. Beiting, "Coherent anti-Stokes Raman scattering velocity and translational temperature measurements in resistojets," Appl. Opt. 36, 3565-3576 (1997)