Detection of nitrogen dioxide by CW cavity-enhanced spectroscopy

摘要

In the paper, an accurate and sensitive system was used to monitor the ambient atmospheric NO_2 concentrations. This system utilizes cavity attenuated phase shift spectroscopy (CAPS), a technology related to cavity ring down spectroscopy (CRDS). Advantages of the CAPS system include such as: (1) cheap and easy to control the light source, (2) high accuracy, and (3) low detection limit. The performance of the CAPS system was evaluated by measuring of the stability and response of the system. The minima (～0.08 ppb NO_2) in the Allan plots show the optimum average time (～100s) for optimum detection performance of the CAPS system. Over a 20-day-long period of the ambient atmospheric NO_2 concentrations monitoring, a comparison of the CAPS system with an extremely accurate and precise chemiluminescence-based NOx analyzer showed that the CAPS system was able to reliably and quantitatively measure both large and small fluctuations in the ambient nitrogen dioxide concentration. The experimental results show that the measuring instrument results correlation is 0.95.