Abstract
The development of increasingly sensitive and robust instruments and new methodologies are essential to improve our understanding of the Earth’s climate and air pollution. In this context, Dual-Comb spectroscopy (DCS) has been successfully demonstrated as a remote laser-based instrument to probe infrared absorbing species such as greenhouse gases. We present here a study of the sensitivity of Dual-Comb spectroscopy to remotely monitor atmospheric gases focusing on molecules that absorb in the ultraviolet domain, where the most reactive molecules of the atmosphere (OH, HONO, BrO...) have their highest absorption cross-sections. We assess the achievable signal-to-noise ratio (SNR) and the corresponding minimum absorption sensitivity of DCS in the ultraviolet range. We propose a potential light source for remote sensing UV-DCS and discuss the degree of immunity of UV-DCS to atmospheric turbulences. We show that the characteristics of the currently available UV sources are compatible with the unambiguous identification of UV absorbing gases by UV-DCS.
Highlights
We first estimate the quality factor Q = M/σf of the UV-Dual-Comb spectroscopy (DCS) spectrometer defined as the signal/noise ratio per spectral element achieved with 1 s acquisition time
The present paper shows that UV-DCS offers, by its fast acquisition rate, the required immunity to atmospheric turbulence for trace-gas concentration monitoring in the atmosphere
UV-DCS allows the multi-trace detection that is necessary for trace gases remote sensing
Summary
The impact of atmospheric pollution on environment, climate, and human health continues to escalate on a global scale [1] despite considerable progress made to develop air-quality monitoring and to provide worldwide environmental policies. Greater knowledge involves a better understanding of the fundamental physical and chemical processes of the atmosphere, a better understanding of the composition of the atmosphere and the development of more sensitive monitoring devices for the minor and very reactive compounds like the hydroxyl radical OH In this context, air pollution measurement and monitoring devices based on absorption spectroscopy contribute significantly. Different experimental arrangements have been developed covering the ultraviolet (UV) out to the infrared (IR) using coherent or non-coherent light sources: Differential Optical Absorption spectroscopy (DOAS) [6], Fourier-Transform Infrared (FTIR) spectroscopy [7], Cavity-Ring Down spectroscopy (CRDS) [8,9,10], and Differential Absorption Lidar (DIAL) [11,12] The advantage of these methodologies when they are coupled with a remote sensing technique is that atmospheric compounds can be probed in situ without air sampling. A sensitivity study of the DCS method in the UV range is presented in Section 5 for the two case-studies
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