CO2 and N2 jets issuing into air from small rectangular channels of 2 x 25 mm cross section were investigated. Concentration measurements were obtained by cw laser Raman spectroscopy; gradients larger than 10 vol. %/100 pm could easily be resolved; spatial resolution was better than 10-2 mm3 and the measured fluctuations of the Raman signals show satisfactory agreement with Poisson statistics. Axial and radial profiles are reported for single and multiple jets and comparison with theory is given, where possible.
"Experimental Investigation Of Small Single And Multiple Free Jets By Laser Raman Spectroscopy," Optical Engineering 18(4), 184409 (1 August 1979). https://doi.org/10.1117/12.7972396