A study of OH radicals in an atmospheric AC discharge plasma using near infrared diode laser cavity ringdown spectroscopy combined with optical emission spectroscopy |
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Authors: | N Srivastava C Wang and T S Dibble |
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Institution: | (1) Department of Physics and Astronomy, and Institute for Clean Energy Technology, Mississippi State University, Starkville, MS 39759, USA;(2) Department of Chemistry, State University of New York College of Environmental Science and Forestry, Syracuse, NY 13210, USA |
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Abstract: | Simultaneous measurements of absolute concentrations of H2O and OH
radicals in an atmospheric AC discharge using continuous wave cavity
ringdown spectroscopy (cw-CRDS) are reported. Formation of OH radicals and
plasma temperatures are characterized by optical emission spectroscopy. The
concentration of OH radical at the edge of the discharge plume at 380 K is
measured by the cw-CRDS technique to be 1.1 ×1015 molecule
cm-3. Ringdown measurements of the H2O (120-000) band and the OH
first overtone around 1515 nm enable us to determine an OH generation yield,
, to be 4.8 ×10-3, where
NOH and are the number densities of OH and H2O,
respectively. The minimum detectable absorption coefficient of the
cw-CRDS system is 8.9 ×10-9 cm-1, which corresponds to a
1σ detection limit of OH number density of 1.2 ×1013 molecule cm-3 in the discharge. This experimental approach is
demonstrated for the first time ever in an AC discharge, and can be applied
in general to a variety of atmospheric plasmas to help study OH formation
mechanisms and OH-related plasma applications. |
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Keywords: | PACS" target="_blank">PACS 52 25 -b Plasma properties 52 70 kz Optical (ultraviolet visible infrared) measurements 52 77 -j Plasma applications 52 70 -m Plasma diagnostic techniques and instrumentation |
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