Experiment research on ellipsoidal structure methane using the absorption characteristics of 3.31 μm mid-infrared spectroscopy

The intensity distribution of absorption spectroscopy of methane mid-infrared fundamental absorption bands, near-infrared combination band of v2 + 2v3 and overtone band of 2v3 were discussed in details in this paper. Quantitative data showed that the absorption intensities of fundamental bands are twice larger than overtone bands, and three times larger than combination bands. Based on the methane 3.31 μm (v3) fundamental absorption bands and differential signal disposal method, a rotational ellipsoidal light structure was designed using ordinary light source and detector to improve gas detection sensitivity. The experimental results of concentration detection showed that the precision of concentration measurement can reach 3% and detection sensitivity is 50 ppm. Meanwhile, experiment was performed to investigate the influence of temperature on mid-infrared absorption performance of methane and the experience curve of 3.31 μm (v3) fundamental absorption signal depending on temperature and its rate of change was drawn.