Laser-fluorescence imaging of O_2 in combustion flows using an ArF laser

Planar laser-induced fluorescence images of O2 in flames have been acquired using an ArF excimer laser as the excitation source. The 193-nm radiation excites several rovibronic lines of the O2 Schumann–Runge (B3∑u− ← X3∑g−) band system. The resultant fluorescence is detected with an image-intensified 100 × 100 photodiode array camera. Images from several CH4/air flames are presented. High-speed sequences of images have been acquired using the high-repetition-rate capability of the excimer laser. These sequences display the real-time evolution of discrete flame structures. The dependence of the fluorescence signal on temperature and O2 concentration is discussed.