Energetics of Molecular Excitation, Fragmentation, and Polymerization in a Dielectric Barrier Discharge with Argon Carrier Gas

We report experiments at atmospheric pressure (AP) using a dielectric barrier discharge (DBD) reactor designed for plasma polymerization (PP) with "monomers" at ‰ concentrations in ca.10 standard liters per minute of argon (Ar) carrier gas. We have perfected a method for measuring Eg, the energy dissipated per cycle of the applied a.c. high voltage, Va(f), but the focus here is on ΔEg, the energy difference with and without a flow, Fd, of monomer in the Ar flow, with the plasma being sustained at Va(f) = 2.8 kVrms, f = 20 kHz. From ΔEg and Fd, we derive a characteristic energy per molecule, Em (in eV), and investigate plots of Em versus Fd and 1/Fd for three model "monomers": formic, acetic, and acrylic acid. These data, along with those for lighter or heavier organic compounds, reveal novel information about energy absorption from the plasma and ensuing polymerization reactions.