The short residence time of Ar-HMDSO (Ar-hexamethyldisiloxane) gas mixtures rapidly flowing across atmospheric-pressure, glow-type, single-filament dielectric barrier discharges is utilized to accomplish thin-film deposition via a purely ionic route. A comparison of thin-film volumes obtained from profilometry, on the one hand, and from the transferred charge, on the other hand, enables to evaluate the mass of the ions contributing to the film growth. For HMDSO fractions at the lower end of the studied range of molar fractions, 50 ppm, pentamethyldisiloxanyl cations (Me 3 SiOSiMe 2 + , PMDS +), generated from the monomer via Penning ionization by Ar(1s) species, are mainly responsible for film formation. For HMDSO fractions growing beyond 1,000 ppm, ionic oligomerization processes by reactions of PMDS + with HMDSO molecules result in a 2.5-fold increase of the average deposited ion mass.

Dielectric-barrier discharges (DBDs) in Ar-N 2 mixtures, with N 2 fractions in 0.1-1% range, would be attractive alternatives to DBDs in pure N 2 if energytransfer reactions between Ar(1s) atoms and N 2 molecules were an efficient source of N atoms. Attempts to functionalize polyolefins in flowing postdischarges fed by such DBDs, as well as the search for the First Positive System in the emission spectrum, however, failed. Evidently, the energy-transfer reactions do not produce N atoms. For Ar(1s 3 ) and Ar(1s 5 ) metastable states, this fact has already been reported in the literature. For Ar(1s 2 ) and Ar(1s 4 ) resonant states, a quantitative argument is derived in this paper: energy transfer from Ar(1s) atoms to N 2 molecules is not an efficient source of N atoms.

Number densities of oxygen atoms, nO, in Ar-O2 mixtures with small initial O2 fractions, $${x}_{{O}_{2}}$$ x O 2  < 1%, flowing through a dielectric-barrier discharge (DBD), are calculated using a plug-flow reactor model, presuming that dissociation and excitation of oxygen species are solely driven by energy-transfer from long-lived excited Ar species, collectively denoted as Ar*. The rate by which Ar* species are generated is calculated from the volume density of power dissipated in the DBD. To obtain extended post-discharge (PD) regions with large nO, experiments were performed with $${x}_{{O}_{2}}$$ x O 2  = 100 ppm. For such low O2 fractions, the time-dependence of nO in the DBD and the early PD can be calculated by a closed equation. Calculations are compared with optical emission spectroscopic (OES) results, utilizing the proportionality of O-atom emission intensity at 777.4 nm to nO. O-atom densities in the PD are made accessible to OES using a tandem setup with a second DBD as sensing discharge. Model testing by experiment is based on the functional dependence of nO on DBD-residence time and PD-delay time, respectively. Wall losses of O atoms in asymmetrical DBD reactors are calculated by an alternative to Chantry’s equation. The agreement between O-atom densities attained at the DBD exit and experimental results is generally good while the speed of rise of nO in the discharge is overestimated, due to the assumption of a constant wall-loss frequency, kW. Compared with literature data, kW is orders of magnitude higher in the DBD and at least one order of magnitude lower in the PD.