Determination of Atomic Oxygen in Atmospheric Plasma from Oxygen Isotope Exchange

• Published in: Plasma processes and polymers Vol. 8; no. 9; pp. 859 - 866
• Main Authors: Schiorlin, Milko, Marotta, Ester, Kim, Hyun-Ha, Paradisi, Cristina, Ogata, Atsushi
• Format: Journal Article
• Language: English
• Published: Weinheim WILEY-VCH Verlag 22-09-2011; WILEY‐VCH Verlag; Wiley-VCH
• Subjects: Atmospheric pressure; Atmospherics; Buffers (chemistry); Concentration (composition); Density; Discharge; Exact sciences and technology; mass spectrometry; non-thermal plasma; O density; Optical (ultraviolet, visible, infrared) measurements; oxygen scrambling; Ozone; Physics; Physics of gases, plasmas and electric discharges; Physics of plasmas and electric discharges; Plasma diagnostic techniques and instrumentation; reactive species concentration; Reactors; Oxygen; Surface discharges; Atmospheric pressure; Plasma reactor; Ozone; Mass spectroscopy; Non thermal plasma; Nitrogen; Helium; oxygen scrambling; Atom density; Kinetic model; Plasma diagnostics; reactive species concentration; Optical method; mass spectrometry; non-thermal plasma; 0 density
• ISSN: 1612-8850; 1612-8869; 1612-8869
• DOI: 10.1002/ppap.201100024

Oxygen scrambling is observed when a 1:1 mixture of 16O2 and 18O2 in nitrogen/helium buffer (total O2: 5–20%) is treated at atmospheric pressure in a surface discharge plasma reactor. The statistical isotope distribution (16O2/18O2/16O18O = 1:1:2) is achieved with a very low SIE (i.e., the energy per unit volume). This process, implemented by kinetic simulations, is proposed as a chemical probe for the determination of the average O‐atom density in atmospheric plasmas. It was found that, within the explored composition range (5–20% O2 in N2/He buffer), the average O‐atom density increases with SIE, while it decreases with increasing content of O2 in the gas being treated. In contrast, an opposite trend is observed for ozone production, which increases with the concentration of O2 in the treated gas. These observations are consistent with the known reaction of O‐atoms with O2 to form ozone, which, at constant total pressure, is expected to favor ozone production as the concentration of O2 is increased.
Oxygen scrambling in mixtures of 16O2 and 18O2 diluted in N2/He at atmospheric pressure and room temperature was studied in a surface discharge plasma reactor as a function of energy input. This process, implemented by kinetic simulations, is proposed as a chemical probe for the determination of oxygen atom density, averaged in space and time, in atmospheric plasmas.