Chemical kinetics and density measurements of OH in an atmospheric pressure He + O2+ H2O RF plasma

Alexandra Helene Marie Brigitte Brisset

Chemical kinetics and density measurements of OH in an atmospheric pressure He + O2+ H2O RF plasma

Physics

Research output: Contribution to conference › Poster › peer-review

Abstract

Densities of OH in a RF driven atmospheric-pressure plasma were measured and modelled in a plane-parallel geometry, in helium with small admixtures of oxygen and water vapour (He+O2+H2O) [1]. The OH density is measured under a wide range of conditions by absorption spectroscopy, using an ultra-stable laser-driven broad-band light source [2]. This light source has a high intensity and excellent temporal intensity stability, leading to an absorption baseline variability lower than 2×10-5 over the range of the OH(X)→OH(A) transition (306-311 nm) [2]. This setup allows a detection limit one order of magnitude lower than the typical limit (about 10-3) that can be achieved with the more commonly used UV-LEDs [3]. These measurements are compared with 0D plasma chemical kinetics simulations adapted for high levels of O2 (1%). It was found that the addition of O2 has a weak effect on the OH density because, while atomic oxygen becomes a dominant precursor for the formation of OH, it makes a nearly equal contribution to the loss processes of OH. The small increase in the density of OH with the addition of O2 is instead due to reaction pathways involving increased production of HO2 and O3. The simulations show that the densities of OH, O and O3 can be tailored relatively independently over a wide range of conditions. The densities of O and O3 are strongly affected by the presence of small quantities (0.05%) of water vapour, but further water addition has little effect. Therefore, a greater range and control of the reactive species mix can be obtained by the use of well-controlled multiple gas admixtures, instead of relying on ambient air mixing.

Original language	English
Publication status	Published - 7 Jun 2021

Cite this

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title = "Chemical kinetics and density measurements of OH in an atmospheric pressure He + O2+ H2O RF plasma",

abstract = "Densities of OH in a RF driven atmospheric-pressure plasma were measured and modelled in a plane-parallel geometry, in helium with small admixtures of oxygen and water vapour (He+O2+H2O) [1]. The OH density is measured under a wide range of conditions by absorption spectroscopy, using an ultra-stable laser-driven broad-band light source [2]. This light source has a high intensity and excellent temporal intensity stability, leading to an absorption baseline variability lower than 2×10-5 over the range of the OH(X)→OH(A) transition (306-311 nm) [2]. This setup allows a detection limit one order of magnitude lower than the typical limit (about 10-3) that can be achieved with the more commonly used UV-LEDs [3]. These measurements are compared with 0D plasma chemical kinetics simulations adapted for high levels of O2 (1%). It was found that the addition of O2 has a weak effect on the OH density because, while atomic oxygen becomes a dominant precursor for the formation of OH, it makes a nearly equal contribution to the loss processes of OH. The small increase in the density of OH with the addition of O2 is instead due to reaction pathways involving increased production of HO2 and O3. The simulations show that the densities of OH, O and O3 can be tailored relatively independently over a wide range of conditions. The densities of O and O3 are strongly affected by the presence of small quantities (0.05%) of water vapour, but further water addition has little effect. Therefore, a greater range and control of the reactive species mix can be obtained by the use of well-controlled multiple gas admixtures, instead of relying on ambient air mixing. ",

author = "Brisset, {Alexandra Helene Marie Brigitte}",

year = "2021",

month = jun,

day = "7",

language = "English",

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TY - CONF

T1 - Chemical kinetics and density measurements of OH in an atmospheric pressure He + O2+ H2O RF plasma

AU - Brisset, Alexandra Helene Marie Brigitte

PY - 2021/6/7

Y1 - 2021/6/7

N2 - Densities of OH in a RF driven atmospheric-pressure plasma were measured and modelled in a plane-parallel geometry, in helium with small admixtures of oxygen and water vapour (He+O2+H2O) [1]. The OH density is measured under a wide range of conditions by absorption spectroscopy, using an ultra-stable laser-driven broad-band light source [2]. This light source has a high intensity and excellent temporal intensity stability, leading to an absorption baseline variability lower than 2×10-5 over the range of the OH(X)→OH(A) transition (306-311 nm) [2]. This setup allows a detection limit one order of magnitude lower than the typical limit (about 10-3) that can be achieved with the more commonly used UV-LEDs [3]. These measurements are compared with 0D plasma chemical kinetics simulations adapted for high levels of O2 (1%). It was found that the addition of O2 has a weak effect on the OH density because, while atomic oxygen becomes a dominant precursor for the formation of OH, it makes a nearly equal contribution to the loss processes of OH. The small increase in the density of OH with the addition of O2 is instead due to reaction pathways involving increased production of HO2 and O3. The simulations show that the densities of OH, O and O3 can be tailored relatively independently over a wide range of conditions. The densities of O and O3 are strongly affected by the presence of small quantities (0.05%) of water vapour, but further water addition has little effect. Therefore, a greater range and control of the reactive species mix can be obtained by the use of well-controlled multiple gas admixtures, instead of relying on ambient air mixing.

AB - Densities of OH in a RF driven atmospheric-pressure plasma were measured and modelled in a plane-parallel geometry, in helium with small admixtures of oxygen and water vapour (He+O2+H2O) [1]. The OH density is measured under a wide range of conditions by absorption spectroscopy, using an ultra-stable laser-driven broad-band light source [2]. This light source has a high intensity and excellent temporal intensity stability, leading to an absorption baseline variability lower than 2×10-5 over the range of the OH(X)→OH(A) transition (306-311 nm) [2]. This setup allows a detection limit one order of magnitude lower than the typical limit (about 10-3) that can be achieved with the more commonly used UV-LEDs [3]. These measurements are compared with 0D plasma chemical kinetics simulations adapted for high levels of O2 (1%). It was found that the addition of O2 has a weak effect on the OH density because, while atomic oxygen becomes a dominant precursor for the formation of OH, it makes a nearly equal contribution to the loss processes of OH. The small increase in the density of OH with the addition of O2 is instead due to reaction pathways involving increased production of HO2 and O3. The simulations show that the densities of OH, O and O3 can be tailored relatively independently over a wide range of conditions. The densities of O and O3 are strongly affected by the presence of small quantities (0.05%) of water vapour, but further water addition has little effect. Therefore, a greater range and control of the reactive species mix can be obtained by the use of well-controlled multiple gas admixtures, instead of relying on ambient air mixing.

M3 - Poster

ER -