Caution with spectroscopic NO<sub>2</sub> reference cells (cuvettes)
<p>Spectroscopic measurements of atmospheric trace gases, for example, by differential optical absorption spectroscopy (DOAS), are frequently supported by recording the trace-gas column density (CD) in absorption cells (cuvettes), which are temporarily inserted into the light path. The idea is...
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doaj-336e94eee07f4f95b500d6f4133eda1e2020-11-25T02:02:21ZengCopernicus PublicationsAtmospheric Measurement Techniques1867-13811867-85482019-11-01126259627210.5194/amt-12-6259-2019Caution with spectroscopic NO<sub>2</sub> reference cells (cuvettes)U. Platt0U. Platt1J. Kuhn2J. Kuhn3Institute of Environmental Physics (IUP), Heidelberg University, INF 229, 69120 Heidelberg, GermanyMax Planck Institute for Chemistry, Mainz, GermanyInstitute of Environmental Physics (IUP), Heidelberg University, INF 229, 69120 Heidelberg, GermanyMax Planck Institute for Chemistry, Mainz, Germany<p>Spectroscopic measurements of atmospheric trace gases, for example, by differential optical absorption spectroscopy (DOAS), are frequently supported by recording the trace-gas column density (CD) in absorption cells (cuvettes), which are temporarily inserted into the light path. The idea is to verify the proper functioning of the instruments, to check the spectral registration (wavelength calibration and spectral resolution), and to perform some kind of calibration (absolute determination of trace-gas CDs). In addition, trace-gas absorption cells are a central component in gas correlation spectroscopy instruments. In principle DOAS applications do not require absorption-cell calibration; however, in practice, measurements with absorption cells in the spectrometer's light path are frequently performed.</p> <p>Since <span class="inline-formula">NO<sub>2</sub></span> is a particularly popular molecule to be studied by DOAS, and at the same time it can be unstable in cells, we chose it as an example to demonstrate that the effective CD seen by the instrument can deviate greatly (by orders of magnitude) from expected values. Analytical calculations and kinetic model studies show the dominating influence of photolysis and dimerization of <span class="inline-formula">NO<sub>2</sub></span>. In particular, this means that the partial pressure of <span class="inline-formula">NO<sub>2</sub></span> in the cell matters. However, problems can be particularly severe at high <span class="inline-formula">NO<sub>2</sub></span> pressures (around 10<span class="inline-formula"><sup>5</sup></span> Pa) as well as low <span class="inline-formula">NO<sub>2</sub></span> partial pressures (of the order of a few 100 Pa). Also, it can be of importance whether the cell contains pure <span class="inline-formula">NO<sub>2</sub></span> or is topped up with air or oxygen (<span class="inline-formula">O<sub>2</sub></span>). Some suggestions to improve the situation are discussed.</p>https://www.atmos-meas-tech.net/12/6259/2019/amt-12-6259-2019.pdf |
collection |
DOAJ |
language |
English |
format |
Article |
sources |
DOAJ |
author |
U. Platt U. Platt J. Kuhn J. Kuhn |
spellingShingle |
U. Platt U. Platt J. Kuhn J. Kuhn Caution with spectroscopic NO<sub>2</sub> reference cells (cuvettes) Atmospheric Measurement Techniques |
author_facet |
U. Platt U. Platt J. Kuhn J. Kuhn |
author_sort |
U. Platt |
title |
Caution with spectroscopic NO<sub>2</sub> reference cells (cuvettes) |
title_short |
Caution with spectroscopic NO<sub>2</sub> reference cells (cuvettes) |
title_full |
Caution with spectroscopic NO<sub>2</sub> reference cells (cuvettes) |
title_fullStr |
Caution with spectroscopic NO<sub>2</sub> reference cells (cuvettes) |
title_full_unstemmed |
Caution with spectroscopic NO<sub>2</sub> reference cells (cuvettes) |
title_sort |
caution with spectroscopic no<sub>2</sub> reference cells (cuvettes) |
publisher |
Copernicus Publications |
series |
Atmospheric Measurement Techniques |
issn |
1867-1381 1867-8548 |
publishDate |
2019-11-01 |
description |
<p>Spectroscopic measurements of atmospheric trace gases, for example, by
differential optical absorption spectroscopy (DOAS), are frequently supported
by recording the trace-gas column density (CD) in absorption cells
(cuvettes), which are temporarily inserted into the light path. The idea is
to verify the proper functioning of the instruments, to check the spectral
registration (wavelength calibration and spectral resolution), and to
perform some kind of calibration (absolute determination of trace-gas CDs).
In addition, trace-gas absorption cells are a central component in gas
correlation spectroscopy instruments. In principle DOAS applications do not
require absorption-cell calibration; however, in practice, measurements with
absorption cells in the spectrometer's light path are frequently performed.</p>
<p>Since <span class="inline-formula">NO<sub>2</sub></span> is a particularly popular molecule to be studied by DOAS, and
at the same time it can be unstable in cells, we chose it as an example to
demonstrate that the effective CD seen by the instrument can deviate greatly
(by orders of magnitude) from expected values. Analytical calculations and
kinetic model studies show the dominating influence of photolysis and
dimerization of <span class="inline-formula">NO<sub>2</sub></span>. In particular, this means that the partial
pressure of <span class="inline-formula">NO<sub>2</sub></span> in the cell matters. However, problems can be
particularly severe at high <span class="inline-formula">NO<sub>2</sub></span> pressures (around 10<span class="inline-formula"><sup>5</sup></span> Pa) as well as
low <span class="inline-formula">NO<sub>2</sub></span> partial pressures (of the order of a few 100 Pa). Also, it can
be of importance whether the cell contains pure <span class="inline-formula">NO<sub>2</sub></span> or is topped up
with air or oxygen (<span class="inline-formula">O<sub>2</sub></span>). Some suggestions to improve the situation are
discussed.</p> |
url |
https://www.atmos-meas-tech.net/12/6259/2019/amt-12-6259-2019.pdf |
work_keys_str_mv |
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