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 parts per thousand concentrations in ca.10 standard liters per minute of argon (Ar) carrier gas. We have perfected a method for measuring E-g, the energy dissipated per cycle of the applied a.c. high voltage, V-a(f), but the focus here is on Delta E-g, the energy difference with and without a flow, F-d, of monomer in the Ar flow, with the plasma being sustained at V-a(f) = 2.8 kV(rms), f = 20 kHz. From Delta E-g and F-d, we derive a characteristic energy per molecule, E-m (in eV), and investigate plots of E-m versus F-d and 1/F-d 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.