The effect of collisional quenching of the O 3p3PJstate on the determination of the spatial distribution of the atomic oxygen density in an APPJ operating in ambient air by TALIF

Zhang, S Shiqiang; Gessel, van Afh Bram; Grootel, van Sc Stephen; Bruggeman, Peter

doi:10.1088/0963-0252/23/2/025012

Cited by 32 publications

(22 citation statements)

References 26 publications

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“…This increased effect is due to the primary surface modification species being a reactive radical, likely atomic oxygen. It has been reported that this particular MHz APPJ source produces atomic oxygen densities on the order of 10 16 cm −3 for similar conditions used here . This increased thickness loss rate is further evidence that the type of APPJ source used is critical with respect to the surface effect needed as different reactive species have vastly different surface effects.…”

Section: Resultssupporting

confidence: 69%

Cold Atmospheric Pressure Plasma VUV Interactions With Surfaces: Effect of Local Gas Environment and Source Design

Knoll

Luan

Bartis

et al. 2016

Plasma Process. Polym.

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This study uses photoresist materials in combination with several optical filters as a diagnostic to examine the relative importance of VUV‐induced surface modifications for different cold atmospheric pressure plasma (CAPP) sources. The argon fed kHz‐driven ring‐APPJ showed the largest ratio of VUV surface modification relative to the total modification introduced, whereas the MHz APPJ showed the largest overall surface modification. The MHz APPJ shows increased total thickness reduction and reduced VUV effect as oxygen is added to the feed gas, a condition that is often used for practical applications. We examine the influence of noble gas flow from the APPJ on the local environment. The local environment has a decisive impact on polymer modification from VUV emission as O2 readily absorbs VUV photons.

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Section: Resultssupporting

confidence: 69%

Cold Atmospheric Pressure Plasma VUV Interactions With Surfaces: Effect of Local Gas Environment and Source Design

Knoll

Luan

Bartis

et al. 2016

Plasma Process. Polym.

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“…The lack an O 3 signature in the TALIF signal is consistent with previous work which has shown [O 3 ] to be low near the plasma jet nozzle, and increase with distance from the nozzle [13,28]. Other work has shown that atomic O content is strongest near the nozzle, and decreases with distance from the nozzle [7,11,13,15] is expected to be somewhat smaller than that measured in plasma jets with 1 -5 % O 2 or air in the gas flow [6,7,22]. The atomic oxygen density produced in the plasma jet increases with RF power, a trend that agrees with previous measurements of [O] in other plasma jet systems [22,31].…”

Section: Resultssupporting

confidence: 89%

Two-photon absorption laser induced fluorescence measurement of atomic oxygen density in an atmospheric pressure air plasma jet

Conway

Gogna

Gaman

et al. 2016

Plasma Sources Sci. Technol.

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Photolysis:• A laser is used to dissociate O 2 molecules producing a known atomic oxygen population. The laser pulse also interacts with these O atoms over the course of the pulse causing two-photon excitation. The resulting TALIF signal is recorded. The amount of [O] produced depends on the wavelength, photon fluence and molecular O 2 density [O 2 ] the laser beam interacts with. The dissociation energy of O 2 is 5.17 eV so once the photon energy of the laser exceeds this value [O] will be generated.• Single laser shot:  = 225.6 nm (E photon = 5.5 eV) t Laser = 8 ns  Single photon absorption in the Herzberg continuum of O 2 ( = 3.21  10 -24 cm 2 at 225.6 nm ) Photo-dissociation of O 2  2 O( 3 P) atoms. Fast process (~10 -13 -10 -14 s)  Laser then excites these O atoms via 2-photon absorption  TALIF signalWhere : Photo-dissociation cross section at  Laser : Photon fluence.• Laser pulse energy E pulse : 1.2 mJ • Laser Frequency f: 1.33  10 15 Hz.• Focal spot area A: 6.03  10 -9 m 2 .As the resulting atomic oxygen density is a function of the laser energy, [O] will vary over the course of the laser pulse. The laser pulse has a Gaussian temporal behaviour so the resulting [O] generated will also vary in a Gaussian manner. Using atmospheric oxygen as our calibrating gas (atm. Pressure = 1.013  10 5 Pa, temperature = 300 K, humidity 0.45) the overall atomic oxygen density value at the end of laser pulse [O] Cal is 7.08  10 19 m -3 .• The atomic O produced by photolysis are "hot". E O(hot) = E photon(225.6 nm) -E dissociation = 5.5 -5.17 = 0.33 eV  O fragments have velocities of up to 1411 m/s so some may leave the laser focal zone before twophoton absorption occurs.• t Laser = 8 nm  O hot atoms travel ~ 11.3 m while laser on so ~ 45 % of O hot potentially lost from the focal zone over the duration of the laser pulse.However due to the small mean free path at atmospheric pressures (~ 66 nm) the root mean square diffusion distance x RMS = 4 = 9.95  10 -7 m so only ~ 4.5 % of the atomic O leave the focal zone over the duration of the laser pulse.O atoms in the red zone can potentially leave the laser focal zone and so will not contribute to the TALIF signal recorded• The hot oxygen atoms produced during photolysis will experience enhanced quenching due to their high velocities when compared with O atoms produced in the plasma. This affects the quenching factor Q which will affect the branching ratio a ij = A ij /(A + Q) for the excited state of these "hot" O atoms.

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“…Finally, Raman scattering was used for evaluating the humid air fraction in the argon effluent. More details about these diagnostics and the measurement conditions and procedures can be found in [10][11][12]15].…”

Section: Methodsmentioning

confidence: 99%

“…One can see that the N 2 (A) density exhibits a much more pronounced time modulation than the NO and O ground state densities (see figure 2 above and figure 3 below). Indeed, van Gessel et al [10] and Zhang et al [15] found that both the NO and O ground state densities are not strongly affected by the power modulation and are constant as a function of time.…”

Section: Time Modulation Of the N 2 (A) Densitymentioning

confidence: 99%

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Numerical analysis of the NO and O generation mechanism in a needle-type plasma jet

2014

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In this paper we study two cold atmospheric pressure plasma jets, operating in Ar + 2% air, with a different electrode geometry but with the same power dissipated in the plasma. The density profiles of the biomedically active NO and O species throughout the plasma jet, previously obtained by laser diagnostics, are calculated by means of a zero-dimensional semi-empirical reaction kinetics model. A good agreement between the calculated and measured data is demonstrated. Furthermore, the most probable spatial power distribution in an RF driven plasma jet is obtained for the first time by comparing measured and calculated species density profiles. This was possible due to the strong effect of the power distribution on the NO and O density profiles. In addition the dominant reaction pathways for both the NO and the O species are identified. The model allows us to obtain key information on the reactive species production inside the jet, which is difficult to access by laser diagnostics in a coaxial geometry. Finally, we demonstrate that water impurities in the order of 100 ppm in the gas feed can have a significant effect on the spatial distribution of the NO and O density.

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The effect of collisional quenching of the O 3p³P_Jstate on the determination of the spatial distribution of the atomic oxygen density in an APPJ operating in ambient air by TALIF

Cited by 32 publications

References 26 publications

Cold Atmospheric Pressure Plasma VUV Interactions With Surfaces: Effect of Local Gas Environment and Source Design

Cold Atmospheric Pressure Plasma VUV Interactions With Surfaces: Effect of Local Gas Environment and Source Design

Two-photon absorption laser induced fluorescence measurement of atomic oxygen density in an atmospheric pressure air plasma jet

Numerical analysis of the NO and O generation mechanism in a needle-type plasma jet

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