Simultaneous detection of C<sub>2</sub>H<sub>6</sub>, CH<sub>4</sub>, and <i>δ</i><sup>13</sup>C-CH<sub>4</sub> using optical feedback cavity-enhanced absorption spectroscopy in the mid-infrared region: towards application for dissolved gas measurements
<p>Simultaneous measurement of <span class="inline-formula">C<sub>2</sub>H<sub>6</sub></span> and <span class="inline-formula">CH<sub>4</sub></span> concentrations, and of the <span class="inline-formula&qu...
| Main Authors: | , , , , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2019-06-01
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| Series: | Atmospheric Measurement Techniques |
| Online Access: | https://www.atmos-meas-tech.net/12/3101/2019/amt-12-3101-2019.pdf |
| Summary: | <p>Simultaneous measurement of <span class="inline-formula">C<sub>2</sub>H<sub>6</sub></span> and <span class="inline-formula">CH<sub>4</sub></span>
concentrations, and of the <span class="inline-formula"><i>δ</i><sup>13</sup>C</span>-<span class="inline-formula">CH<sub>4</sub></span> isotope ratio is
demonstrated using a cavity-enhanced absorption spectroscopy technique in
the mid-IR region. The spectrometer is compact and has been designed for
field operation. It relies on optical-feedback-assisted injection of
3.3 <span class="inline-formula">µ</span>m radiation from an interband cascade laser (ICL) into a V-shaped
high-finesse optical cavity. A minimum absorption coefficient of <span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M10" display="inline" overflow="scroll" dspmath="mathml"><mrow><mn mathvariant="normal">2.8</mn><mo>×</mo><msup><mn mathvariant="normal">10</mn><mrow><mo>-</mo><mn mathvariant="normal">9</mn></mrow></msup></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="51pt" height="14pt" class="svg-formula" dspmath="mathimg" md5hash="bdc4c13b8c1b479b84979c848c76cc46"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="amt-12-3101-2019-ie00001.svg" width="51pt" height="14pt" src="amt-12-3101-2019-ie00001.png"/></svg:svg></span></span> cm<span class="inline-formula"><sup>−1</sup></span> is obtained in a single scan (0.1 s) over 0.7 cm<span class="inline-formula"><sup>−1</sup></span>. Precisions of 3 ppbv, 11 ppbv, and 0.08 ‰ for
<span class="inline-formula">C<sub>2</sub>H<sub>6</sub></span>, <span class="inline-formula">CH<sub>4</sub></span>, and <span class="inline-formula"><i>δ</i><sup>13</sup>C</span>-<span class="inline-formula">CH<sub>4</sub></span>, respectively, are
achieved after 400 s of integration time. Laboratory calibrations and tests
of performance are reported here. They show the potential for the
spectrometer to be embedded in a sensor probe for in situ measurements in ocean
waters, which could have important applications for the understanding of the
source and fate of hydrocarbons from the seabed and in the water column.</p> |
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| ISSN: | 1867-1381 1867-8548 |