Two‐dimensional average concentration measurements in a jet flow by Raman scattering

A multipass cell arrangement and a low‐light‐level television camera were used to obtain a simultaneous digitized two‐dimensional concentration profile of CH4 flowing from an axisymmetric jet by measuring the spontaneous Raman radiation. Because the Raman technique is species selective, the concentration profile of the N2 contained in the surrounding gas (air) was also determined for CH4 and SF6 jets under the same conditions. Comparison is made with the concentration profiles determined by Mie scattering in seeded jets.