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Extramural Research

Grantee Research Project Results

Grantee Research Project Results

Resolution of Overlapping Spectra by Wavelength Modulation Spectroscopy

EPA Grant Number: U914936
Title: Resolution of Overlapping Spectra by Wavelength Modulation Spectroscopy
Investigators: Bullock, Audra M.
Institution: Old Dominion University
EPA Project Officer: Jones, Brandon
Project Period: January 1, 1996 through July 9, 2001
Project Amount: $68,000
RFA: STAR Graduate Fellowships (1996)
Research Category: Academic Fellowships , Engineering and Environmental Chemistry , Fellowship - Electrical Engineering



The overall objective of this research project is to show that wavelength modulation is a convenient means of increasing the sensitivity of an absorption spectroscopy measurement because it allows for harmonic detection. The specific objectives of this research project are to: (1) determine the resolution of overlapping spectra by harmonic detection; and (2) the advantages gained by performing detection at the higher harmonics (e.g., sixth and eighth).


Wavelength modulation absorption spectroscopy is a highly sensitive, nonintrusive technique for probing gaseous species, which employs the well-known principles of modulation spectroscopy in a novel way. With this technique, parameters such as velocity, density, and temperature can be measured with a high degree of precision.

Additionally, it is shown that the higher harmonic detection orders can be used to identify transition line shape profiles as well as absorption line parameters. A study of the line shape profile for the oxygen A-band transitions is presented. This research also examined general characteristics of absorption signals obtained by employing wavelength modulation spectroscopy with harmonic detection are discussed along with their corresponding applications.

The results of this study indicate that oxygen exhibits collisional narrowing on the order of 0.006 cm-1 atm-1 in this near-infrared atmospheric band.

Supplemental Keywords:

fellowship, wavelength modulation spectroscopy, harmonic detection, Scientific Discipline, Air, Environmental Monitoring, Engineering, Chemistry, & Physics, Environmental Engineering, harmonic detection, air sampling

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The perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Conclusions drawn by the principal investigators have not been reviewed by the Agency.

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