https://doi.org/10.1140/epjd/e2009-00174-9
A study of OH radicals in an atmospheric AC discharge plasma using near infrared diode laser cavity ringdown spectroscopy combined with optical emission spectroscopy
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
Corresponding author: a cw175@msstate.edu
Received:
18
March
2009
Revised:
30
April
2009
Published online:
16
June
2009
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.
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
© EDP Sciences, Società Italiana di Fisica, Springer-Verlag, 2009