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Dissociative attachment in selected monochloroalkanes
Abstract
The total cross sections for the dissociative attachment (DA) process have been measured for nine normal chloroalkanes, ${\rm C\sb{n}H\sb{2n+1}Cl}$ for n = 1-9, for two secondary compounds, 2-chloropropane and 2-chlorobutane, one tertiary compound, t-butyl chloride, and three cyclic chloroalkanes, ${\rm c-C\sb{n}H\sb{2n-1}Cl}$ for n = 4-6 for electron energies below 4 eV. This has been accomplished with a newly constructed apparatus incorporating a trochoidal monochromator as the source of the electron beam and a uniquely long collision chamber to minimize the percentage of ions lost at the ends. Except for methyl chloride, all of the compounds studied produced a single broad DA peak located between 1.3 eV and 1.6 eV. The magnitudes of the peaks varied by a factor of approximately 30 from the smallest, 1-chloropropane, to the largest, t-butyl chloride. The DA peak cross section in methyl chloride was found to be significantly smaller than the peaks in the other compounds and shifted toward much lower energy. It is believed that this measurement may still be limited by the presence of impurities and that the true peak magnitude may be even smaller. Using vertical attachment energies (VAE) determined by electron transmission spectroscopy elsewhere and in this work, we show that the resonance widths vary linearly with VAE in this series of compounds and that the peak DA cross sections decline exponentially with increasing VAE. Also included are observations of the temperature effects on the DA cross sections of methyl chloride and other selected chloroalkanes. These were performed using a second apparatus with crossed electron and effusive molecular beams. As the vibrational temperatures of the compounds were increased, two peaks, one near zero energy and the other at 0.8 eV, became visible and grew in magnitude. The peak at 0.8 eV is attributed to the production of HCl by decomposition of the chloroalkanes on the walls of the oven. The temperature dependence of the peak near zero energy in methyl chloride is discussed in detail and compared to the results of recent theoretical calculations.
Subject Area
Molecules|Analytical chemistry
Recommended Citation
Pearl, Donald Mark, "Dissociative attachment in selected monochloroalkanes" (1994). ETD collection for University of Nebraska-Lincoln. AAI9504145.
https://digitalcommons.unl.edu/dissertations/AAI9504145