Laser & Optoelectronics Progress, Volume. 56, Issue 19, 193003(2019)
Analytical Method of Spectral Overlapping Interference Using Laser Absorption Spectroscopy
Laser absorption spectroscopy is widely used for monitoring trace gases in the atmosphere. However, some gases have several overlapping absorption lines. Therefore, the peak signals overlap; this affects the measured results. For example, the NH3 peak near 6529 cm -1 includes four overlapping absorption lines. Absorption spectra at different pressures are simulated to obtain four absorption lines separated by Voigt-line profiles. First, the experimental platform is established by the direct absorption method. The experiment demonstrates that the peak value of the NH3 spectra at low gas concentration does not decrease. However, the peak value increases at a lower gas pressure. The phenomenon may be attributed to the absorbability of NH3. Therefore, the CH4 gas, which does not exhibit absorbability, is used to verify this assumption. Finally, by analyzing the NH3 absorption lines at different pressures, it is determined that the difference between the experimental and simulated spectra is the smallest when the gas pressure is 0.18 atm(≈18 kPa)and the maximum absorption peak of NH3 is proportional to the gas concentration. This result solves the interference problem, which will improve future gas-detection approaches.
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Li Xu, Zhirong Zhang, Fengzhong Dong, Pengshuai Sun, Hua Xia, Runqing Yu, Zhe Li, Qiming Xu. Analytical Method of Spectral Overlapping Interference Using Laser Absorption Spectroscopy[J]. Laser & Optoelectronics Progress, 2019, 56(19): 193003
Category: Spectroscopy
Received: Mar. 12, 2019
Accepted: Apr. 19, 2019
Published Online: Oct. 23, 2019
The Author Email: Zhang Zhirong (zhangzr@aiofm.ac.cn)