Quenching rate constants for reactions of Ar(4p′[1/2], 4p[1/2], 4p[3/2]2, and 4p[5/2]2) atoms with 22 reagent gases

Sadeghi, N.; Setser, D. W.; Francis, A.; Czarnetzki, Uwe; Döbele, H. F.

doi:10.1063/1.1388037

Cited by 110 publications

(70 citation statements)

References 91 publications

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“…The agreement with results from TALIF measurements at krypton [7] and argon [8] is very good. The PROES measurements based on electron impact excitation are, in contrast to laser measurements, not limited by optical selection rules or large energy gaps between the ground and excited state.…”

Section: Lifetimes and Quenching Coefficientssupporting

confidence: 77%

Prospects of Phase Resolved Optical Emission Spectroscopy as a Powerful Diagnostic Tool for RF‐Discharges

Gans

Gathen²,

Döbele³

2004

Contrib. Plasma Phys.

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Phase resolved optical emission spectroscopy (PROES) bears considerable potential for diagnostics of RF discharges. It allows for detailed investigations of spatial and temporal variations of excitation processes. Based on phase and space resolved measurements of the population dynamics of excited states several diagnostic techniques have been developed. Results for a hydrogen capacitively coupled RF (CCRF) discharge are discussed as an example. The gas temperature, the degree of dissociation and the temporally and spatially resolved electron energy distribution function (EEDF) of energetic electrons (>12eV) are measured. Furthermore, the pulsed electron impact excitation during the field reversal phase, typical for hydrogen CCRF discharges, is exploited for measurements of atomic and molecular data like lifetimes of excited states, coefficients for radiationless collisional de-excitation (quenching coefficients), and cascading processes from higher electronic states. IntroductionRF discharges bear considerable application potential [1]. Measurements by quantitative nonintrusive optical emission spectroscopy (OES) are fairly complicated due to pronounced spatial and temporal (during the RF cycle) variations of various excitation processes. Temporal variations are not considered in the standard corona model commonly used for OES of stationary low-density plasmas, since it is based on balance equations only. Phase resolved OES (PROES) requires a time dependent model based on rate equations. An analytical model for the population dynamics within the RF cycle has been developed. The model takes into account: electron impact excitation, heavy particle collisional excitation, radiationless collisional de-excitation (quenching), radiation trapping and cascading processes from higher electronic states [2].Measurements are performed in an asymmetric CCRF discharge excited at 13.56 MHz in hydrogen with small admixtures of rare gases. The flat, cooled electrodes are 25 mm apart and 100 mm in diameter. Figure 1 displays the excitation dynamics of the n=3 level of atomic hydrogen along the discharge axis. The abscissa comprises two RF periods (74ns each). Structures I and II are caused by electron impact excitation during the field reversal phase, typical for hydrogen CCRF discharges, and the sheath expansion phase respectively [3]. Structure III results from fast secondary electrons created by ion impact at the powered electrode and ionisation in the sheath region [4]. Structure IV is related to heavy particle collisional excitation of energetic (>100eV) hydrogen atoms created at the electrode surface by impact of hydrogen ions [5].

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Section: Lifetimes and Quenching Coefficientssupporting

confidence: 77%

Prospects of Phase Resolved Optical Emission Spectroscopy as a Powerful Diagnostic Tool for RF‐Discharges

Gans

Gathen²,

Döbele³

2004

Contrib. Plasma Phys.

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“…The rate constants for quenching of Ar 4 p states by N 2 , O 2 , and Ar are, depending on the 4 p state considered, 0.3-3.5 Â 10 À10 cm 3 s À1 , 4.6-7.6 Â 10 À10 cm 3 s À1 , and 1.2-1.6 Â 10 À11 cm 3 s À1 , respectively. 44 In pure Ar plasma, at atmospheric pressure and T ¼ 400 K, the quenching rate of Ar 4 p states by Ar atoms is 2.1-2.9 Â 10 8 s À1 , i.e., about ten times larger than the radiative frequency (2.5-4.5 Â 10 7 s À1 (Ref. 45)).…”

Section: B Influence Of Ambient Air On the Flowing Afterglowmentioning

confidence: 99%

Influence of ambient air on the flowing afterglow of an atmospheric pressure Ar/O2 radiofrequency plasma

Duluard

Dufour

Hubert

et al. 2013

Journal of Applied Physics

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International audienceThe influence of ambient air on the flowing afterglow of an atmospheric pressure Ar/O2 radiofrequency plasma has been investigated experimentally. Spatially resolved mass spectrometry and laser induced fluorescence on OH radicals were used to estimate the intrusion of air in between the plasma torch and the substrate as a function of the torch-to-substrate separation distance. No air is detected, within the limits of measurement uncertainties, for separation distances smaller than 5 mm. For larger distances, the effect of ambient air can no longer be neglected, and radial gradients in the concentrations of species appear. The Ar 4p population, determined through absolute optical emission spectroscopy, is seen to decrease with separation distance, whereas a rise in emission from the N2(C–B) system is measured. The observed decay in Ar 4p and N2(C) populations for separation distances greater than 9mm is partly assigned to the increasing collisional quenching rate by N2 and O2 molecules from the entrained air. Absorption measurements also point to the formation of ozone at concentrations from 10^14 to 10^15 cm-3, depending both on the injected O2 flow rate and the torch-to-substrate separation distance

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“…We can infer the effective quenching rate on the basis of measured quenching coefficients, since we know the dominant colliders responsible for quenching of the laser excited oxygen atoms as well as their density distributions. Under the conditions investigated molecular oxygen is the dominant quenching partner [24].…”

Section: Two-photon Absorption Laser-induced Fluorescencementioning

confidence: 99%

Optical Diagnostics of Micro Discharge Jets

Gathen

Buck

Gans

et al. 2007

Contrib. Plasma Phys.

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Micro plasmas operated at ambient pressure with dimensions of the confining geometry in the order of a few ten micrometers to a millimeter are actually in the focus of interest due to the broad regime of applicability they offer and due to a similarly broad range of open physical questions. Here we present optical measurements within the discharge core and the effluent region of an especially developed micro discharge jet. To get an understanding of the complex system of this discharge it is important to analyse transport phenomena of energy and particles within both parts of the discharge by various highly sophisticated diagnostics. As a consequence of the limited access and the dimensions of the micro discharge most of these diagnostics are optical. Here we present diagnostics applied to determine spatially resolved absolute atomic oxygen densities as the most reactive constituent of the effluent, density maps of ozone as final reaction product of the gas chemical chain induced by the discharge and phase resolved optical emission spectroscopy yielding insight into the excitation dynamics of the discharge.

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Quenching rate constants for reactions of Ar(4p′[1/2], 4p[1/2], 4p[3/2]2, and 4p[5/2]2) atoms with 22 reagent gases

Cited by 110 publications

References 91 publications

Prospects of Phase Resolved Optical Emission Spectroscopy as a Powerful Diagnostic Tool for RF‐Discharges

Prospects of Phase Resolved Optical Emission Spectroscopy as a Powerful Diagnostic Tool for RF‐Discharges

Influence of ambient air on the flowing afterglow of an atmospheric pressure Ar/O2 radiofrequency plasma

Optical Diagnostics of Micro Discharge Jets

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