Photoionization mass spectrometry of combustion radicals. Final technical report Page: 18 of 26
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candidates for the m/z=96 signal. The
fact that only 1,1-DCE is observed
provides a useful clue to the mechanism
by which 1,1-DCE is formed. Indeed,
this observation is consistent with the
conclusion of Tsang and Walker that
H-atom addition followed by Cl-atom
elimination dominates abstraction of Cl
by H for chloroethylenes at the flame
temperatures of interest here. 1,1-DCE
is formed when an H atom addition and
Cl elimination occurs at the carbon site
on the H-atom end of trichloroethylene.
In contrast to the photoionization
efficiency curves for CH3 and 1,1-DCE,
a PIE curve with a slowly increasing
linear variation above threshold is
observed for m/z =112 as shown in Fig.
24. In this case an accurate
determination of the ionization threshold
9.80 9.82 9.84 9.86
Photon Energy (eV)
Figure 23: Semilogarithmic PIE curve for
would require a knowledge of the vibronic
wavefunctions for neutral and cation to account for the unresolved structure
responsible for the gradually rising PIE cur
and m/z = 114 exhibit similar PIE curves
and that these signals have strengths
consistent with the relative isotopic
abundances of 35CI35Ol and 5CI37CI
isotopomers suggests that these signals
correspond to dichloroethenol C2H20Cl2
with the structure
suggested by Kirchner, eta/., formed
by OH addition to and CI elimination
from trichloroethylene. Here again the
channel dominates the possible
abstraction of an H atom by OH.
Although the low resolution of our
measurements restricts the accuracy of
The fact that signals at both m/z = 112
.8 . v
i..* .*...*.. .. .
9.10 9.5 9.20 9.25 9.30
Photon Energy (eV)
Figure 24: Photoionization efficiency
curve for dichloroethenol.
1 . . 1 . . I
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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/m1/18/: accessed January 17, 2019), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.