Photoionization mass spectrometry of combustion radicals. Final technical report Page: 2 of 26
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Fundamental research on the combustion of halogenated organic compounds with
emphasis on reaction pathways leading to the formation of chlorinated organic
compounds and the development of continuous emission monitoring methods will
assist in DOE efforts in the management and control of hazardous chemical wastes.
Selective laser ionization techniques are used in our laboratory for the measurement
of concentration profiles of radical intermediates in chlorinated hydrocarbon flames.
A novel flame-sampling VUV laser photoionization mass spectrometer, constructed
with DOE funding, is in use for these studies. Progress is reported here on the use
of this new facility in the development, refinement, and verification of chemical
kinetic models describing the thermal destruction of toxic chlorocarbons commonly
found in chemical wastes.
The use of VUV laser photoionization mass spectrometry for flame species profile
measurements has important advantages over other laser-based techniques (LIF,
REMPI, laser absorption spectroscopy) and conventional electron-impact ionization
* This new approach largely avoids parent ion fragmentation
problems, has a sensitivity comparable to LIF and REMPI methods, and
requires no prior spectroscopic information.
* Measurements of mass resolved photoionization efficiency (PIE)
curves, inherent in this approach, provide a high degree of species
selectivity, which is quite important in the complex flame species
* The PIE measurements yield low resolution ( 0.01 eV) estimates of
ionization potentials, which are often useful for the identification of
In contrast to the LIF and REMPI methods, VUV laser ionization mass spectrometry
may yield absolute rather than relative species concentration profiles with the use
of reliable calibration methods, similar in concept to those currently in use with
conventional electron-impact ionization mass spectrometry. Indeed, a major focus
of our recent effort has been the development of photoionization efficiency
calibrations, needed for accurate absolute determinations of flame species
In the past two years we have used the flame sampling VUV laser ionization mass
spectrometer system for studies of chlorocarbon-doped methane/oxygen flames.
Relative concentration profiles and photoionization efficiency curves have been
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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/m1/2/: accessed November 19, 2018), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.