scholarly journals Mobile and high-spectral-resolution Fabry–Pérot interferometer spectrographs for atmospheric remote sensing

2021 ◽  
Vol 14 (12) ◽  
pp. 7873-7892
Author(s):  
Jonas Kuhn ◽  
Nicole Bobrowski ◽  
Thomas Wagner ◽  
Ulrich Platt
Keyword(s):  
Remote Sensing ◽  
High Resolution ◽  
Absorption Spectroscopy ◽  
Spectral Resolution ◽  
Trace Gases ◽  
Resolving Power ◽  
Trace Gas ◽  
Oh Radicals ◽  
Fabry Perot ◽  
Atmospheric Trace Gas

Abstract. Grating spectrographs (GS) are presently widely in use for atmospheric trace gas remote sensing in the ultraviolet (UV) and visible spectral range (e.g. differential optical absorption spectroscopy, DOAS). For typical DOAS applications, GSs have a spectral resolution of about 0.5 nm, corresponding to a resolving power R (ratio of operating wavelength to spectral resolution) of approximately 1000. This is sufficient to quantify the vibro-electronic spectral structure of the absorption of many trace gases with good accuracy and further allows for mobile (i.e. compact and stable) instrumentation. However, a much higher resolving power (R≈105, i.e. a spectral resolution of about the width of an individual rotational absorption line) would facilitate the measurement of further trace gases (e.g. OH radicals), significantly reduce cross interferences due to other absorption and scattering processes, and provide enhanced sensitivity. Despite these major advantages, only very few atmospheric studies with high-resolution GSs are reported, mostly because increasing the resolving power of a GS leads to largely reduced light throughput and mobility. However, for many environmental studies, light throughput and mobility of measurement equipment are central limiting factors, for instance when absorption spectroscopy is applied to quantify reactive trace gases in remote areas (e.g. volcanoes) or from airborne or space-borne platforms. For more than a century, Fabry–Pérot interferometers (FPIs) have been successfully used for high-resolution spectroscopy in many scientific fields where they are known for their superior light throughput. However, except for a few studies, FPIs have hardly received any attention in atmospheric trace gas remote sensing, despite their advantages. We propose different high-resolution FPI spectrograph implementations and compare their light throughput and mobility to GSs with the same resolving power. We find that nowadays mobile high-resolution FPI spectrographs can have a more than 2 orders of magnitude higher light throughput than their immobile high-resolution GS counterparts. Compared with moderate-resolution GSs (as routinely used for DOAS), an FPI spectrograph reaches a 250 times higher spectral resolution while the signal-to-noise ratio (SNR) is reduced by only a factor of 10. Using a first compact prototype of a high-resolution FPI spectrograph (R≈148 000, <8 L, <5 kg), we demonstrate that these expectations are realistic. Using mobile and high-resolution FPI spectrographs could have a large impact on atmospheric near-UV to near-infrared (NIR) remote sensing. Applications include the enhancement of the sensitivity and selectivity of absorption measurements of many atmospheric trace gases and their isotopologues, the direct quantification of OH radicals in the troposphere, high-resolution O2 measurements for radiative transfer and aerosol studies, and solar-induced chlorophyll fluorescence quantification using Fraunhofer lines.

scholarly journals Mobile and high spectral resolution Fabry Pérot interferometer spectrographs for atmospheric remote sensing

2021 ◽  
Author(s):  
Jonas Kuhn ◽  
Nicole Bobrowski ◽  
Thomas Wagner ◽  
Ulrich Platt
Keyword(s):  
Remote Sensing ◽  
High Resolution ◽  
Absorption Spectroscopy ◽  
Spectral Resolution ◽  
Trace Gases ◽  
Resolving Power ◽  
Trace Gas ◽  
Oh Radicals ◽  
Fabry Perot ◽  
Atmospheric Trace Gas

Abstract. Grating spectrographs (GS) are presently widely in use for atmospheric trace gas remote sensing in the ultraviolet (UV) and visible spectral range (e.g. differential optical absorption spectroscopy, DOAS). For typical DOAS applications, GSs have a spectral resolution of about half a nm corresponding to a resolving power R (ratio of operating wavelength to spectral resolution) in the range of 1000. This is sufficient to quantify the vibro-electronic spectral structure of the absorption of many trace gases with good accuracy and further allows for mobile (i.e. compact and stable) instrumentation. However, a much higher resolving power (R ≈ 105, i.e. a spectral resolution of about the width of an individual rotational absorption line) would facilitate the measurement of further trace gases (e.g. OH radicals), significantly reduce cross interferences due to other absorption and scattering processes, and provide enhanced sensitivity. Despite of these major advantages, only very few atmospheric studies with high resolution GSs are reported, mostly because increasing the resolving power of a GS leads to largely reduced light throughput and mobility. However, for many environmental studies, light throughput and mobility of measurement equipment are central limiting factors, for instance when absorption spectroscopy is applied to quantify reactive trace gases in remote areas (e.g. volcanoes) or from air borne or space borne platforms. Since more than a century, Fabry Pérot interferometers (FPIs) have been successfully used for high resolution spectroscopy in many scientific fields where they are known for their superior light throughput. However, except for a few studies, FPIs received hardly any attention in atmospheric trace gas remote sensing, despite their advantages. We propose different high resolution FPI spectrograph implementations and compare their light throughput and mobility to GSs with the same resolving power. We find that nowadays mobile high resolution FPI spectrographs can have a more than two orders of magnitude higher light throughput than their immobile high resolution GS counterparts. Compared to moderate resolution GSs (as routinely used for DOAS), a FPI spectrograph reaches a 250 times higher spectral resolution while the signal to noise ratio (SNR) is reduced by only a factor of 10. With a first compact prototype of a high resolution FPI spectrograph (R ≈ 148000, < 8 litres, < 5 kg) we demonstrate that these expectations are realistic. Using mobile and high resolution FPI spectrographs could have a large impact on atmospheric near UV to near IR remote sensing. Applications include the enhancement of sensitivity and selectivity of absorption measurements of many atmospheric trace gases and their isotopes, the direct quantification of OH radicals in the troposphere, high resolution O2 measurements for radiative transfer and aerosol studies and solar induced chlorophyll fluorescence quantification using Fraunhofer lines.

Towards DOAS measurements with a picometre spectral resolution

2021 ◽  
Author(s):  
Jonas Kuhn ◽  
Nicole Bobrowski ◽  
Thomas Wagner ◽  
Ulrich Platt
Keyword(s):  
Remote Sensing ◽  
High Resolution ◽  
Spectral Resolution ◽  
Trace Gases ◽  
High Resolution Spectroscopy ◽  
Optical Absorption Spectroscopy ◽  
Oh Radicals ◽  
Near Ir ◽  
Atmospheric Remote Sensing ◽  
Moderate Resolution

&lt;p&gt;Differential Optical Absorption Spectroscopy (DOAS) has proven to be very useful to study the composition and dynamics of Earth&amp;#8217;s atmosphere. Compact grating spectrographs (GSs) with moderate spectral resolution (ca. 1nm) allow to quantify the absorption of many trace gases along atmospheric light paths from ground to space borne platforms.&lt;/p&gt;&lt;p&gt;Since the width of a rovibronic absorption line of a small molecule in the UV to near IR spectral range is in the picometre range, increasing the spectral resolution of DOAS measurements largely increases their selectivity and in many cases also their sensitivity. In addition, further trace gases (e.g. OH radicals) or isotopes of trace gases could be detected, while common problems due to Fraunhofer line undersampling were reduced. However, since high resolution GSs are bulky (immobile) instruments with a strongly reduced light throughput, hardly any high resolution DOAS measurements have been performed.&lt;/p&gt;&lt;p&gt;Since more than a century, Fabry P&amp;#233;rot Interferometers (FPIs) have been successfully used for high resolution spectroscopy in many scientific fields, where their light throughput advantage over grating spectrographs for higher resolving powers is well known. However, except for a few studies, FPIs&lt;br&gt;received hardly any attention in atmospheric trace gas remote sensing. We examine the light throughput of GSs and FPI spectrographs regarding spectral resolution and spectrograph size (i.e. mobility). We find that robust and mobile high resolution FPI spectrograph implementations can be by orders of magnitude smaller than GSs with the same spectral resolution. A compact high resolution FPI spectrograph prototype was already successfully tested in the field. Further, the light throughput can be optimised to allow for passive scattered sunlight measurements with similar SNR as moderate resolution DOAS measurements while, at the same time, attaining spectral resolutions in the picometre range.&lt;/p&gt;&lt;p&gt;High resolution FPI spectrographs might allow for a multitude of applications in atmospheric remote sensing. A few examples include scattered sunlight absorption measurements of many atmospheric trace gases and their isotopes, the quantification of tropospheric and volcanic OH radicals, high resolution O2 measurements for radiative transfer investigation and aerosol studies, and solar induced chlorophyll fluorescence quantification using Fraunhofer lines.&lt;/p&gt;

scholarly journals Automated fragment formula annotation for electron ionisation, high resolution mass spectrometry: application to atmospheric measurements of halocarbons

2021 ◽  
Vol 13 (1) ◽  
Author(s):  
Myriam Guillevic ◽  
Aurore Guillevic ◽  
Martin K. Vollmer ◽  
Paul Schlauri ◽  
Matthias Hill ◽  
...  
Keyword(s):  
Mass Spectrometry ◽  
Data Analysis ◽  
High Resolution ◽  
High Resolution Mass Spectrometry ◽  
Trace Gases ◽  
Trace Gas ◽  
Atmospheric Measurements ◽  
High Resolution Mass ◽  
Atmospheric Trace Gas ◽  
Resolution Mass

Abstract Background Non-target screening consists in searching a sample for all present substances, suspected or unknown, with very little prior knowledge about the sample. This approach has been introduced more than a decade ago in the field of water analysis, together with dedicated compound identification tools, but is still very scarce for indoor and atmospheric trace gas measurements, despite the clear need for a better understanding of the atmospheric trace gas composition. For a systematic detection of emerging trace gases in the atmosphere, a new and powerful analytical method is gas chromatography (GC) of preconcentrated samples, followed by electron ionisation, high resolution mass spectrometry (EI-HRMS). In this work, we present data analysis tools to enable automated fragment formula annotation for unknown compounds measured by GC-EI-HRMS. Results Based on co-eluting mass/charge fragments, we developed an innovative data analysis method to reliably reconstruct the chemical formulae of the fragments, using efficient combinatorics and graph theory. The method does not require the presence of the molecular ion, which is absent in $$\sim$$ ∼ 40% of EI spectra. Our method has been trained and validated on >50 halocarbons and hydrocarbons, with 3–20 atoms and molar masses of 30–330 g mol$$^{-1}$$ - 1 , measured with a mass resolution of approx. 3500. For >90% of the compounds, more than 90% of the annotated fragment formulae are correct. Cases of wrong identification can be attributed to the scarcity of detected fragments per compound or the lack of isotopic constraint (no minor isotopocule detected). Conclusions Our method enables to reconstruct most probable chemical formulae independently from spectral databases. Therefore, it demonstrates the suitability of EI-HRMS data for non-target analysis and paves the way for the identification of substances for which no EI mass spectrum is registered in databases. We illustrate the performances of our method for atmospheric trace gases and suggest that it may be well suited for many other types of samples. The L-GPL licenced Python code is released under the name ALPINAC for ALgorithmic Process for Identification of Non-targeted Atmospheric Compounds.

Effect of Spectral Resolution on Measurement of Trace Gases in Atmosphere by Differential Optical Absorption Spectroscopy

2008 ◽  
Vol 28 (9) ◽  
pp. 1643-1648
Author(s):  
彭夫敏 彭夫敏 ◽  
谢品华 谢品华 ◽  
张英华 张英华 ◽  
李海洋 李海洋 ◽  
司福祺 司福祺 ◽  
...  
Keyword(s):  
Optical Absorption ◽  
Absorption Spectroscopy ◽  
Spectral Resolution ◽  
Trace Gases ◽  
Differential Optical Absorption Spectroscopy ◽  
Optical Absorption Spectroscopy

scholarly journals Application of Near-Infrared Optical Feedback Cavity Enhanced Absorption Spectroscopy (OF-CEAS) to the Detection of Ammonia in Exhaled Human Breath

Sensors ◽  
2019 ◽  
Vol 19 (17) ◽  
pp. 3686
Author(s):  
Zhifu Luo ◽  
Zhongqi Tan ◽  
Xingwu Long
Keyword(s):  
Detection Limit ◽  
Absorption Spectroscopy ◽  
Spectral Resolution ◽  
Optical Feedback ◽  
Low Pressure ◽  
High Spectral Resolution ◽  
Trace Gas ◽  
Human Breath ◽  
Enhanced Absorption ◽  
Cavity Enhanced Absorption Spectroscopy

The qualitative and quantitative analysis to trace gas in exhaled human breath has become a promising technique in biomedical applications such as disease diagnosis and health status monitoring. This paper describes an application of a high spectral resolution optical feedback cavity enhanced absorption spectroscopy (OF-CEAS) for ammonia detection in exhaled human breath, and the main interference of gases such as CO2 and H2O are approximately eliminated at the same time. With appropriate optical feedback, a fibered distributed feedback (DFB) diode laser emitting at 1531.6 nm is locked to the resonance of a V-shaped cavity with a free spectral range (FSR) of 300 MHz and a finesse of 14,610. A minimum detectable absorption coefficient of αmin = 2.3 × 10−9 cm−1 is achieved in a single scan within 5 s, yielding a detection limit of 17 ppb for NH3 in breath gas at low pressure, and this stable system allows the detection limit down to 4.5 ppb when the spectra to be averaged over 16 laser scans. Different from typical CEAS with a static cavity, which is limited by the FSR in frequency space, the attainable spectral resolution of our experimental setup can be up to 0.002 cm−1 owing to the simultaneous laser frequency tuning and cavity dither. Hence, the absorption line profile is more accurate, which is most suitable for low-pressure trace gas detection. This work has great potential for accurate selectivity and high sensitivity applications in human breath analysis and atmosphere sciences.

Development of an incoherent broadband cavity-enhanced absorption spectroscopy (IBBCEAS) instrument for autonomous field measurements of HONO and NO2 in a rural area

2021 ◽  
Author(s):  
Lingshuo Meng ◽  
Gaoxuan Wang ◽  
Cécile Coeur ◽  
Alexandre Tomas ◽  
Tao Wu ◽  
...  
Keyword(s):  
Rural Area ◽  
Absorption Spectroscopy ◽  
Atmospheric Chemistry ◽  
Nitrous Acid ◽  
Trace Gases ◽  
Ambient Air ◽  
Rural Site ◽  
Oh Radicals ◽  
Enhanced Absorption ◽  
Cavity Enhanced Absorption Spectroscopy

&lt;p&gt;Nitrous acid (HONO) is one of the important atmospheric trace gases due to its contribution to the cycles of nitrogen oxides (NOx) and hydrogen oxides (HOx). In particular it acts as a precursor of tropospheric OH radicals, which is responsible for the self-cleansing capacity of the atmosphere [1,2]. We developed an instrument based on incoherent broadband cavity enhanced absorption spectroscopy (IBBCEAS) for automatic measurement of HONO in a rural area in a summer period during a field &quot;Campagne d&amp;#8217;OBservation Intensive des Ae&amp;#769;rosols et pre&amp;#769;curseurs a&amp;#768; Caillou&amp;#235;l-Cr&amp;#233;pigny (COBIACC)&quot; in France. IBBCEAS technique is now extensively used in field applications for the measurements of both trace gases and aerosols [3,4].&lt;/p&gt;&lt;p&gt;Real-time in situ measurements of HONO and NO&lt;sub&gt;2&lt;/sub&gt; have been simultaneously carried out. The IBBCEAS instrument performance has been demonstrated and validated through lab-based tests, and in particular through field intercomparison via side-by-side measurements of temporal concentration profiles of HONO and NO&lt;sub&gt;2&lt;/sub&gt; in the rural area. The intercomparison of the concentration measurements between IBBCEAS and an instrument called MARGA (Monitor for AeRosols and Gases in Ambient air) for HONO, and IBBCEAS vs. a reference NOx analyzer for NO&lt;sub&gt;2&lt;/sub&gt;. Good agreements have been observed which demonstrated the performance of the developed IBBCEAS instrument for the measurement of atmospheric HONO concentration (&lt;5 ppb) in a rural area.&lt;/p&gt;&lt;p&gt;The preliminary experimental results will be presented and discussed.&lt;/p&gt;&lt;p&gt;&lt;strong&gt;Acknowledgments&lt;/strong&gt; This work was supported by the CPER CLIMIBIO program and the Labex CaPPA project (ANR-10-LABX005). The authors highly appreciate the offers of Mr. Eric Wetzels from Polyfluor Plastics bv for the help in our instrumental conception involving Teflon pipe.&lt;/p&gt;&lt;p&gt;&lt;strong&gt;References&lt;/strong&gt;&lt;/p&gt;&lt;p&gt;[1] X. Li, T. Brauers, R. H&amp;#228;seler, R. Bohn, H. Fuchs, A. Hofzumahaus, F. Holland, S. Lou, et al., Exploring the atmospheric chemistry of nitrous acid (HONO) at a rural site in Southern China, Atmos. Chem. Phys. &lt;strong&gt;12&lt;/strong&gt; (2012) 1497-1513.&lt;/p&gt;&lt;p&gt;[2] H. Su, Y. Cheng, M. Shao, D. Gao, Z. Yu, L. Zeng, J. Slanina, et al., Nitrous acid (HONO) and its daytime sources at a rural site during the 2004 PRIDE&amp;#8208;PRD experiment in China, J. Geophys. Res. &lt;strong&gt;113&lt;/strong&gt; (2008) D14312.&lt;/p&gt;&lt;p&gt;[3] T. Wu, Q. Zha, W. Chen, Z. Xu, T. Wang, X. He, Development and deployment of a cavity enhanced UV-LED spectrometer for measurements of atmospheric HONO and NO&lt;sub&gt;2&lt;/sub&gt; in Hong Kong, Atmos. Environ. &lt;strong&gt;95&lt;/strong&gt; (2014) 544-551.&lt;/p&gt;&lt;p&gt;[4] L. Meng, G. Wang, P. Augustin, M. Fourmentin, Q. Gou, E. Fertein, T. N. Ba, C. Coeur, A. Tomas, W. Chen, Incoherent broadband cavity enhanced absorption spectroscopy-based strategy for direct measurement of aerosol extinction in lidar blind zone, Opt. Lett. &lt;strong&gt;45 &lt;/strong&gt;(2020) 1611-1614.&lt;/p&gt;

The spherical Fabry—Perot interferometer as an instrument of high resolving power for use with external or with internal atomic beams

1961 ◽  
Vol 263 (1314) ◽  
pp. 289-308 ◽  
Keyword(s):  
High Resolution ◽  
Hyperfine Structure ◽  
Atomic Beam ◽  
Resonance Line ◽  
Resolving Power ◽  
Light Power ◽  
Line Structure ◽  
Fabry Perot ◽  
Atomic Beams ◽  
Very High

The spherical Fabry -Perot interferometer was designed by P. Connes as an instrument capable of realizing higher resolving power than the normal Fabry -Perot interferometer, by virtue of its greater light power at high resolution, and the much lower requirement with regard to accuracy of adjustment. The instrument has now been used successfully in the resolution of structure in the resonance line of the arc spectrum of barium; components with a separation of 2.0x 10 -3 cm -1 have been resolved; they were observed in the absorption produced by a Jackson -Kuhn atomic beam, of high collimation. The instrument has also been used for observing line structure with an absorbing atomic beam traversing the interior of the interferometer; by this means the amount of material required for observing hyperfine structure using an atomic beam , even with very high collimation, can be reduced to a few milligrams, or approximately 100 times less than that required with an atomic beam external to the interferometer, so that enriched isotopes, available in small quantities, can be used; alternatively, adequate absorption can be obtained with much higher collimations of the beam, and correspondingly improved limits of resolution.

scholarly journals High Resolution Interference Spectroscopy Applied to Astronomical Investigations (2000 to 3000 Å)

1971 ◽  
Vol 41 ◽  
pp. 262-262
Author(s):  
B. Bates
Keyword(s):  
High Resolution ◽  
Time Resolution ◽  
Spectroscopic Studies ◽  
Resolving Power ◽  
Angular Dispersion ◽  
Fabry Perot

For orbiting astronomical telescopes and for spectroscopic studies from rocket and balloon-borne platforms the great angular dispersion of the Fabry-Pérot interferometer should permit easier guidance tolerance for a given spectral resolving power with the added profit of the physical compactness of an etalon spectrometer or spectrograph. In addition, the superiority in luminosity and illumination of the interferometer permits shorter exposures and greater time resolution.

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