Effect of Nitrogen dioxide for environmental gas detection using Pulsed Cavity ring down spectroscopy
Citation
Y. Seetha Mahalakshmi, P. Madhusudana Rao, S. Surendra Babu "Effect of Nitrogen dioxide for environmental gas detection using Pulsed Cavity ring down spectroscopy", International Journal of Engineering Trends and Technology (IJETT), V45(10),531-533 March 2017. ISSN:2231-5381. www.ijettjournal.org. published by seventh sense research group
Abstract
Global climate awareness is an
important prerequisite for the benefit of the living
species. A balance of the green house gases would
make the terrestrial climate friendly and problem
free. In this context ground based spectroscopic
measurement of atmospheric gases play a major
role .Nitrogen oxides present in the atmosphere
react with water leading to acid rains. Atmospheric
photo chemistry induces a complicated mechanism
between Nitrogen oxides which impact the Ozone
abundance. Detection of environmental gases by
optical methods have proved to be the fastest and
reliable detection techniques and Cavity Ring Down
Spectroscopy in particular has proved to meet the
requirements of being non invasive , portable,
instantaneous and precise without interference with
other species. It can detect weak absorptions as well
as diluted species. The use of high reflectivity
mirrors of the order of 99.99% enables the increase
in effective path lengths of the light within the cavity
and hence contribute to ultra high sensitivities. The
purpose of this paper is to emphasis on Nitrogen Di
oxide ,an important green house gas. Theoretical
simulations are performed for NO2 at two different
wavelengths(447 nm and 532 nm) based on the
technique of Cavity ring down spectroscopy(CRDS).
The empty cavity ring down time constant ?0 and the
concentration dependant ring down time constant ?
are obtained through simulations. The analysis is
done for increasing cavity lengths from 40 cm to 90
cm at 447 nm and 532 nm. The results have shown
that the time constant difference (?0 - ?) increases
with gas concentration and is unique at each
wavelength due to the dependence on absorption
cross-section.
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Keywords
Cavity ring down
spectroscopy(CRDS), time constant ,parts per
billion(ppb),Absorption cross-section, Nitrogen di
oxide, Beer-Lamberts law.