Diagnostic based modeling for determining absolute atomic oxygen densities in atmospheric pressure helium-oxygen plasmas

Abstract

Absolute atomic oxygen ground state densities in a radio-frequency driven atmospheric pressure plasma jet, operated in a helium-oxygen mixture, are determined using diagnostic based modeling. One-dimensional numerical simulations of the electron dynamics are combined with time integrated optical emission spectroscopy. The population dynamics of the upper O 3p P3 (λ=844 nm) atomic oxygen state is governed by direct electron impact excitation, dissociative excitation, radiation losses, and collisional induced quenching. Absolute values for atomic oxygen densities are obtained through comparison with the upper Ar 2p1 (λ=750.4 nm) state. Results for spatial profiles and power variations are presented and show excellent quantitative agreement with independent two-photon laser-induced fluorescence measurements.

Investigation of the radially resolved oxygen dissociation degree and local mean electron energy in oxygen plasmas in contact with different surface materials

“…[12][13][14][15][16][17][18][19][20][21][22][23][24][25] This makes it particularly difficult to accurately control the densities of highly reactive species, such as atomic oxygen, in industrial processing applications. Previous investigations have sought insight into these processes by measuring the density of atomic oxygen and its surface recombination probability for various materials using twophoton absorption laser-induced fluorescence (TALIF), 12,[26][27][28][29][30] optical emission spectroscopy (OES), 21,22,[31][32][33][34] and VUV absorption spectroscopy. 23,35,36 TALIF and VUV absorption are well known for their accuracy, however, both are challenging to implement in industrial plasma reactors, particularly if spatially resolved measurements are required.…”

“…Various works have extended the basic actinometry approach for atomic oxygen (and atomic hydrogen 38 ) to incorporate the dissociative excitation process. [32][33][34] In order to do this, argon is typically used as a tracer gas with the emission from the Ar(2p 1 …”

“…Several works have demonstrated this coupling of experimental observations and simulations to be a reliable method of determining the atomic oxygen density in both high and low pressure plasma sources. [32][33][34] Here, we apply a further extension of the described techniques, known as Energy Resolved Actinometry (ERA) in order to measure atomic oxygen densities and local mean electron energies simultaneously and with high spatial resolution. This technique has been described in detail and benchmarked for the case of an atmospheric pressure plasma jet by Greb et al 41 Briefly, the ERA approach, which is inclusive of direct and dissociative excitation processes, modifies the commonly used actinometry technique in two significant ways (i) to additionally include atomic oxygen emission from the O(3p 5 P) excited state at k ¼ 777.4 nm and (ii) to utilise excitation ratios in place of emission intensity ratios.…”

The influence of surface properties on the plasma dynamics in radio-frequency driven oxygen plasmas: Measurements and simulations

“…New concepts for process control and plasma monitoring have been developed based on the combination of numerical simulations and advanced plasma diagnostics. [1][2][3] The influence of surface condition on the plasma dynamics is investigated by means of numerical simulations of a capacitively coupled oxygen rf discharge. The surface loss probability of singlet delta molecular oxygen (SDO) is varied to investigate the corresponding impact on the plasma parameters and associated excitation features.…”

The effects of a helium based RF microplasma with small additions of O<inf>2</inf>, Ar and N<inf>2</inf> on plasmid DNA

“…The plasma was operated with constant moderate power. The singlet delta oxygen, ozone and atomic oxygen densities in this source have been measured [3,4].The effect of plasma exposure to plasmid DNA was studied. Damage was considered to be an event wherein a single or double strand break was created.…”