Photoionization mass spectrometry of combustion radicals. Final technical report Page: 21 of 26
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1. A sub-ppm detection sensitivity is achieved (similar to that of REMPI or LIF).
2. Mass-resolved measurements of photoionization efficiencies are an integral
part of the technique. These measurements ensure selective detection of a
given species present in a complex background of other flame species.
3. This approach largely avoids fragmentation problems common to
conventional electron-impact mass spectrometry. In exceptional cases (0, H,
OH, CI, C2Cl2, HCl) target species have ionization potentials that exceed those
of potential precursor parent species, and difficulties are encountered with
4. This method is versatile. No prior spectroscopic information is required for
species detection and identification. Three types of ionization may be used in
the same apparatus. Besides direct single photon VUV photoionization, both
REMPI and laser-induced electron impact ionization may be employed.
5. The technique is convenient for low resolution ( 0.01-0.02 eV)
measurements of ionization potentials of radical intermediates. In many cases
these measurements are useful in making species identifications (e.g., species
with similar or identical m/z values).
A major goal of our research is the development of useful kinetic models of the
combustion of a few selected chlorocarbons (trichloroethylene, chloroform, methyl
chloride) with particular emphasis on precursor pathways that lead to the formation
of toxic combustion byproducts. The identification of reaction intermediates and
quantitative determinations of their concentration profiles in well-defined laboratory
flames are essential inputs to this model development effort.
The Appendices to this report present detailed results obtained for the chemistry of
flames containing trichloroethylene, during the final year of this program. These
results are contained in the two papers:
1. J. H. Werner and T. A. Cool., "The Combustion of Trichloroethylene Studied
with VUV Photoionization Mass Spectrometry", Twenty-Seventh Symposium
(International) on Combustion, The Combustion Institute, (1998), pp. 413-423.
2. J. H. Werner and T. A. Cool, "The Kinetics of the Combustion of
Trichloroethylene for Low CI/H Ratios", Combustion and Flame, in press.
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Cool, T.A. Photoionization mass spectrometry of combustion radicals. Final technical report, report, December 31, 1998; United States. (digital.library.unt.edu/ark:/67531/metadc684924/m1/21/: accessed October 18, 2018), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.