Optical emission spectroscopy as a diagnostic for plasmas in liquids: opportunities and pitfalls
Peter Bruggeman
Tiny Verreycken
Manuel A. Gonzalez
James L. Walsh
Michael G. Kong
Christophe Leys
Daan C. Schram
2134/6389
https://repository.lboro.ac.uk/articles/journal_contribution/Optical_emission_spectroscopy_as_a_diagnostic_for_plasmas_in_liquids_opportunities_and_pitfalls/9547994
In this contribution, optical emission spectroscopy is evaluated and thoroughly analysed as a
diagnostic to characterize plasmas in and in contact with liquids. One of the specific properties
of plasmas in and in contact with liquids is the strong emission of OH(A–X) and of hydrogen
lines. As an example a 600 ns pulsed dc excited discharge in Ar, He and O2 bubbles in water is
investigated by time resolved optical emission spectroscopy. It is shown that the production
processes of excited species and the plasma kinetics strongly influence the emission spectrum.
This complicates the interpretation of the spectra but provides the opportunity to derive
production mechanisms from the time resolved emission. The importance of recombination
processes compared with direct electron excitation processes in the production of excited
states of the water fragments in plasmas with high electron densities is shown. The OH(A–X)
emission spectrum illustrates that even in these highly collisional atmospheric pressure
discharges the rotational population distribution deviates from equilibrium. A two-temperature
fit of the OH rotational population distribution leads to realistic gas temperatures for the
temperature parameter corresponding to small rotational numbers. The Hα and Hβ lines are
fitted with two component profiles corresponding to two different electron densities.
The obtained electron density is in the range 1021–1023 m−3. Possible complications in the
interpretation of obtained temperatures and electron densities are discussed.
2010-06-23 12:51:48
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Mechanical Engineering not elsewhere classified