The direct detection of early chemical intermediates following corona discharges is essential for understanding the chemistry of nonthermal plasma treatment of volatile organic compounds. We used supersonic gas expansions combined with time-of-flight mass spectrometry to stabilize and mass characterize neutral post-discharge intermediates of alkylbenzenes. Initial electron impact events in the discharge should produce fragmentation products. However, using 118 nm 10 ns photoionization pulses, we observed single prominent higher mass post-discharge intermediates, corresponding to addition of CH. The fs photoionization spectra add considerable elucidation, now showing high mass peaks due to successive additions of carbons as well as fragment peaks due to successive losses of carbons. These observations combined with additional experiments indicate that the reactions proceed mainly through neutral species and that higher mass products are not likely formed by ring insertion. The extremely sensitive detection provided by fs photoionization may prove useful in trace analysis of environmentally sensitive compounds.

Novel chemistry in alkylbenzenes following corona discharge: A molecular beam study

239th National Meeting (2010)

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