Diode laser detection of greenhouse gases in the near-infrared region by wavelength modulation spectroscopy: pressure dependence of the detection sensitivity.

Takashi Asakawa,Nozomu Kanno,Kenichi Tonokura

doi:10.3390/s100504686

Takashi Asakawa, Nozomu Kanno + Show 1 more

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https://doi.org/10.3390/s100504686

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Abstract

We have investigated the pressure dependence of the detection sensitivity of CO2, N2O and CH4 using wavelength modulation spectroscopy (WMS) with distributed feed-back diode lasers in the near infrared region. The spectral line shapes and the background noise of the second harmonics (2f) detection of the WMS were analyzed theoretically. We determined the optimum pressure conditions in the detection of CO2, N2O and CH4, by taking into consideration the background noise in the WMS. At the optimum total pressure for the detection of CO2, N2O and CH4, the limits of detection in the present system were determined.

Highlights

Atmospheric pollution is a problem as global warming is caused by the man-made addition of extra amounts of greenhouse gases such as CO2, N2O and CH4
We assumed that background noise was linearly dependent on M2, according Equation (9), and the simulated noise intensities were normalized to minimize the residual to experimental values
In the wavelength modulation spectroscopy (WMS), optimization of the signal intensity occurs at ΔF/half width at half maximum (HWHM) = 2.2 in the Voigt function to calculate the properties of the 2f line shape [21]

Summary

Introduction

Atmospheric pollution is a problem as global warming is caused by the man-made addition of extra amounts of greenhouse gases such as CO2, N2O and CH4. CO2 is released into the atmosphere when fossil fuels, coal, solid waste and wood products are burned, during cement production, and when land surface cover is changed by humans. Increased CH4 levels come from fossil fuels, rice cultivation, animal husbandry, biomass burning and landfills. The main anthropogenic sources of N2O are agriculture, and industrial sources including adipic and nitric acid production. Combustion of solid waste and fossil fuels contributes to atmospheric N2O. The need to detect these trace gases has become increasingly important in recent years, both for controlling industrial processes and for monitoring air quality. Since many trace gases have a significant impact on the environment, the development of techniques for its fast, accurate and sensitive detection is required [1,2,3,4,5]

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