Dual–pump CARS for the simultaneous detection of N₂, O₂ and CO in CH₄ flames

The application of a modified dual‐pump CARS set‐up for the simultaneous determination of temperature and N 2 , O 2 and CO concentration is demonstrated. This technique offers numerous advantages, which are discussed in detail and presented for the investigation of a partially premixed flame. In comparison with a standard vibrational CARS set‐up, consisting of one Nd:YAG laser and one broadband dye laser together with a single spectrometer and camera, only one additional narrowband dye laser is needed. By shifting the spectral profile of the broadband dye laser providing the excitation profile, N 2 and CO were excited simultaneously from a single narrowband–broadband laser combination as in an usual CARS set‐up with degenerate pump wavenumbers. Additionally, oxygen was excited using the same broadband laser but another narrowband laser in a dual‐pump CARS configuration. The technique presented is not limited to the three species investigated here.