Effect of Nitrogen dioxide for environmental gas detection using Pulsed Cavity ring down spectroscopy

  IJETT-book-cover  International Journal of Engineering Trends and Technology (IJETT)          
  
© 2017 by IJETT Journal
Volume-45 Number-10
Year of Publication : 2017
Authors : Y. Seetha Mahalakshmi, P. Madhusudana Rao, S. Surendra Babu
DOI :  10.14445/22315381/IJETT-V45P300

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.