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Detection of nitric oxide at low ppb center dot m concentrations by differential absorption spectrometry using a fully diode-laser-based ultraviolet laser system
Umeå University, Faculty of Science and Technology, Physics.
Umeå University, Faculty of Science and Technology, Physics.
Umeå University, Faculty of Science and Technology, Physics.
Umeå University, Faculty of Science and Technology, Physics.
2007 (English)In: Journal of the Optical Society of America B, Vol. 24, no 9, 2294-2306 p.Article in journal (Refereed) Published
Abstract [en]

An instrumentation for detection of nitric oxide (NO) by direct absorption spectrometry in the parts in 109 (ppb) range on its electronic X2 Pi(v(n) = 0)-A(2)Sigma(+)(v' = 0) transition has been constructed around a commercially available fully diode-laser-based laser system producing milliwatts powers of ultraviolet light at similar to 226.6 run, and its analytical performance has been evaluated. It is shown that the system is capable of detecting NO down to 3 ppb . m under low-pressure conditions (at a signal-to-noise ratio of 3 for a signal averaging of 5s), which is 2 orders of magnitude below that of any other diode-laser-based absorption technique. The combined line strength of the targeted lines was assessed to 3.1 X 10(-18) cm(-1)/(molecule cm(-2)), which supersedes typical line strengths of the fundamental vibrational band and the first and second overtone bands of NO by similar to 2, similar to 4, and similar to 5 orders of magnitude, respectively Also the collision broadening and shift of the targeted lines in NO by N-2 have been assessed.

Place, publisher, year, edition, pages
2007. Vol. 24, no 9, 2294-2306 p.
National Category
Atom and Molecular Physics and Optics
Identifiers
URN: urn:nbn:se:umu:diva-8605OAI: oai:DiVA.org:umu-8605DiVA: diva2:148276
Available from: 2008-01-30 Created: 2008-01-30 Last updated: 2011-05-10Bibliographically approved
In thesis
1. Development of diode laser-based absorption and dispersion spectroscopic techniques for sensitive and selective detection of gaseous species and temperature
Open this publication in new window or tab >>Development of diode laser-based absorption and dispersion spectroscopic techniques for sensitive and selective detection of gaseous species and temperature
2011 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The main aim of this thesis has been to contribute to the ongoing work with development of new diode-laser-based spectroscopic techniques and metho­do­lo­gies for sensitive detection of molecules in gas phase. The techniques under scrutiny are tunable diode laser absorption spectrometry (TDLAS) and Faraday modulation spectrometry (FAMOS). Conventional distributed-feedback (DFB) tele­communication diode lasers working in the near-infrared (NIR) region have been used for detection of carbon monoxide (CO) and temperature in hot humid media whereas a unique frequency-quadrupled external-cavity diode laser producing mW powers of continuous-wave (cw) light in the ultra violet (UV) region have been used for detection of nitric oxide (NO).

A methodology for assessment of CO in hot humid media by DFB-TDLAS has been developed. By addressing a particular transition in its 2nd overtone band, and by use of a dual-fitting methodology with a single reference water spectrum for background correction, % concentrations of CO can be detected in media with tens of percent of H2O (≤40%) at T≤1000 °C with an accuracy of a few %. Moreover, using an ordinary DFB laser working in the C-band, a technique for assessment of the temperature in hot humid gases (T≤1000 °C) to within a fraction of a percent has been developed. The technique addresses two groups of lines in H2O that have a favorable temperature dependence and are easily accessed in a single scan, which makes it sturdy and useful for industrial applications.

A technique for detection of NO on its strong electronic transitions by direct absorption spectrometry (DAS) using cw UV diode laser light has been deve­loped. Since the electronic transitions are ca. two or several orders of magnitude stronger than of those at various rotational-vibra­tional bands, the system is capable of detecting NO down to low ppb∙m concentrations solely using DAS.

Also the FAMOS technique has been further developed. A new theoretical description expressed in terms of both the integrated line strength of the transition and 1st Fourier coefficients of a magnetic-field-modulated dispersive lineshape functions is presented. The description has been applied to both ro-vib Q-transitions and electronic transitions in NO. Simulations under different pressures and magnetic field conditions have been made that provide the optimum conditions for both cases. A first demonstration and characteri­zation of FAMOS of NO addressing its electronic transitions in the UV-region has been made, resulting in a detection limit of 10 ppb∙m. The characterization indicates that the technique can be significantly improved if optimum conditions can be obtained, which demonstrates the high potential of the UV-FAMOS technique.

Place, publisher, year, edition, pages
Umeå: Umeå University, Department of Physics, 2011. 118 p.
Keyword
Absorption Spectrometry (AS), Wavelengh Modulation Absorption Spectrometry (WMAS), Faraday Modulation Spectrometry (FAMOS), Tunable Diode Laser Absorption Spectrometry (TDLAS)
National Category
Atom and Molecular Physics and Optics
Research subject
Physics
Identifiers
urn:nbn:se:umu:diva-43799 (URN)978-91-7459-190-3 (ISBN)
Public defence
2011-06-08, Naturvetarhuset, N420, Umeå universitet, Umeå, 10:00 (English)
Opponent
Supervisors
Available from: 2011-05-13 Created: 2011-05-10 Last updated: 2011-05-10Bibliographically approved

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