Photoionization mass spectrometry of combustion radicals. Final technical report Page: 19 of 26
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threshold determinations, we estimate
the ionization potential of dichloroethenol
to be 9.08 0.02 eV from the data of
Fig. 24. This estimate is obtained by a
linear extrapolation of the PIE curve to
the baseline at 9.05 0.02 eV, to which
we add 0.02 eV to account for internal
excitation effects at the rotational
temperature (T 160K) of the molecular
beam, and an additional 0.01 eV to
account for Rydberg state field
ionization. Two other structural isomers
of C2H2OC2, dichloroacetaldehyde and
chloroacetylchloride (cf. Fig. 25), have
respective ionization potentials of 10.5
and 11.0 eV, but no previous
measurements of the ionization potential
of dichloroethenol are available.
3 Isomers of C2 H20CI2
A q -38 k=u00n (grou diVil eads)
AN -4 90 5 kcuiA.2 (mm.w...
I.P. U 1.5OV (ltuwaw)
Table V summarizes the threshold $c
ionization energies we have obtained q -
from the PIE curves for a number of
flame species. In every case the CS""'1""11id
threshold energies are in very good -" - 2 ocA1 (Mea.no
agreement with precise values taken I.P.-11.0. ",, LsrNwa m"
from the literature. Although the
thresholds determined from the PIE Figure 25: Three isomers of C2H20C12.
curves are of limited accuracy ( 0.01-
0.02 eV) compared with those measured spectroscopically with various techniques
(e.g., PES, REMPI, ZEKE, MATI, PIRI), they are nonetheless quite useful for species
identification. In some cases the flame zone may be a convenient source of new
radical species for which no previous ionization potential measurements exist; the PIE
curves may then be expected to yield approximate ( 0.02 eV) values, which may
provide a convenient reference for more precise studies.
IV. SUMMARY OF COMPLETED WORK
In our work to date we have demonstrated that flame-sampling VUV laser
photoionization mass spectrometry is a valuable new method for recording relative
concentration profiles for reaction intermediates in laboratory flames. The method
offers several advantages:
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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/m1/19/: accessed July 21, 2018), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.