Detection of Ammonia Using Logarithmic-Transformed Wavelength Modulation Spectrum

4th Annual International Workshop on Materials Science and Engineering

Cong, Menglong^1 ; Sun, Dandan^1

College of Physics and Electronic Information, Inner Mongolia University for the Nationalities, No.22, Huolinhe street, Tongliao, Inner Mongolia, China^1

关键词: Combination bands;    Differential detection;    Effective path lengths;    Intensity modulations;    Logarithmic transformations;    Residual amplitude modulation;    Wavelength modulation;    Wavelength modulation spectroscopy;   

Others  :  https://iopscience.iop.org/article/10.1088/1757-899X/381/1/012132/pdf
DOI  :  10.1088/1757-899X/381/1/012132

来源: IOP

【 摘 要 】

Conventional wavelength modulation spectroscopy is improved by logarithmic-transformed data processing and differential detection for trace gas sensing. The optic intensity modulation is isolated from the gas absorption induced laser power attenuation via the logarithmic-transformation, and then it is balanced out by differential detection. The theory is validated by the detection of P(6) NH3-absorption line belonging to the ν3 + ν4 combination band in a stainless tube with effective path length of 24.5 cm, under room temperature (296 K) and atmospheric pressure (1.01e5 Pa). The second harmonic is recovered while the residual amplitude modulation and distortion of harmonic are eliminated.