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<front>
<journal-meta>
<journal-id journal-id-type="publisher">AMTD</journal-id>
<journal-title-group>
<journal-title>Atmospheric Measurement Techniques Discussions</journal-title>
<abbrev-journal-title abbrev-type="publisher">AMTD</abbrev-journal-title>
</journal-title-group>
<issn pub-type="epub">1867-8610</issn>
<publisher><publisher-name>Copernicus GmbH</publisher-name>
<publisher-loc>Göttingen, Germany</publisher-loc>
</publisher>
</journal-meta>
<article-meta>
<article-id pub-id-type="doi">10.5194/amtd-3-2681-2010</article-id>
<title-group>
<article-title>Inherent calibration of a novel LED-CE-DOAS instrument to measure iodine oxide, glyoxal, methyl glyoxal, nitrogen dioxide, water vapour and aerosol extinction in open cavity mode</article-title>
</title-group>
<contrib-group><contrib contrib-type="author" xlink:type="simple"><name name-style="western"><surname>Thalman</surname>
<given-names>R.</given-names>
</name>
<xref ref-type="aff" rid="aff1">
<sup>1</sup>
</xref>
</contrib>
<contrib contrib-type="author" xlink:type="simple"><name name-style="western"><surname>Volkamer</surname>
<given-names>R.</given-names>
</name>
<xref ref-type="aff" rid="aff1">
<sup>1</sup>
</xref>
<xref ref-type="aff" rid="aff2">
<sup>2</sup>
</xref>
</contrib>
</contrib-group><aff id="aff1">
<label>1</label>
<addr-line>Department of Chemistry and Biochemistry, University of Colorado, Boulder, CO 80309, USA</addr-line>
</aff>
<aff id="aff2">
<label>2</label>
<addr-line>Cooperative Institute for Research in the Environmental Sciences CIRES, Boulder, CO 80309, USA</addr-line>
</aff>
<pub-date pub-type="epub">
<day>24</day>
<month>06</month>
<year>2010</year>
</pub-date>
<volume>3</volume>
<issue>3</issue>
<fpage>2681</fpage>
<lpage>2721</lpage>
<permissions>
<license xlink:type="simple">
<license-p>This is an open-access article ditributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.</license-p>
</license>
</permissions>
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<self-uri xlink:href="http://www.atmos-meas-tech-discuss.net/3/2681/2010/amtd-3-2681-2010.pdf">The full text article is available as a PDF file from http://www.atmos-meas-tech-discuss.net/3/2681/2010/amtd-3-2681-2010.pdf</self-uri>
<abstract>
<p>The combination of Cavity Enhanced Absorption Spectroscopy (CEAS) with
broad-band light sources (e.g.  Light-Emitting Diodes, LEDs) lends itself to
the application of cavity enhanced Differential Optical Absorption
Spectroscopy (CE-DOAS) to perform sensitive and selective point measurements
of multiple trace gases and aerosol extinction with a single instrument. In
contrast to other broad-band CEAS techniques, CE-DOAS relies only on the
measurement of relative intensity changes, i.e.  does not require knowledge
of the light intensity in the absence of trace gases and aerosols (I&lt;sub&gt;0&lt;/sub&gt;).
We have built a prototype LED-CE-DOAS instrument in the blue spectral range
(420–490 nm) to measure nitrogen dioxide (NO&lt;sub&gt;2&lt;/sub&gt;), glyoxal (CHOCHO),
methyl glyoxal (CH&lt;sub&gt;3&lt;/sub&gt;COCHO), iodine oxide (IO), water vapour (H&lt;sub&gt;2&lt;/sub&gt;O)
and oxygen dimers (O&lt;sub&gt;4&lt;/sub&gt;). We demonstrate the first CEAS detection of
methyl glyoxal, and the first CE-DOAS detection of CHOCHO and IO. A further innovation
consists in the measurement of extinction losses from the cavity, e.g. due to
aerosols, at two wavelengths by observing O&lt;sub&gt;4&lt;/sub&gt; (477 nm) and H&lt;sub&gt;2&lt;/sub&gt;O (443 nm)  and measuring
the pressure, relative humidity and temperature independently. This approach
is demonstrated by experiments where laboratory aerosols of known size and
refractive index were generated and their extinction measured. The measured
extinctions were then compared to the theoretical extinctions calculated
using Mie theory (3–7&amp;times;10&lt;sup&gt;-7&lt;/sup&gt; cm&lt;sup&gt;-1&lt;/sup&gt;). Excellent agreement is found
from both the O&lt;sub&gt;4&lt;/sub&gt; and H&lt;sub&gt;2&lt;/sub&gt;O retrievals. This enables the first
inherently calibrated CEAS measurement in open cavity mode (mirrors facing
the open atmosphere), and eliminates the need for sampling lines to supply
air to the cavity, and/or keep the cavity enclosed and aerosol free.
Measurements in open cavity mode are demonstrated for CHOCHO, CH&lt;sub&gt;3&lt;/sub&gt;COCHO,
NO&lt;sub&gt;2&lt;/sub&gt;, H&lt;sub&gt;2&lt;/sub&gt;O and aerosol extinction at 477 nm and 443 nm. Our
prototype LED-CE-DOAS provides a low cost, yet research grade innovative
instrument for applications in simulation chambers and in the open
atmosphere.</p>
</abstract>
<counts><page-count count="41"/></counts>
</article-meta>
</front>
<body/>
<back>
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