Electronic quenching of OH(A) by water in atmospheric pressure plasmas and its influence on the gas temperature determination by OH(A–X) emission
- 21 December 2009
- journal article
- Published by IOP Publishing in Plasma Sources Science and Technology
- Vol. 19 (1), 015016
- https://doi.org/10.1088/0963-0252/19/1/015016
Abstract
In this paper it is shown that electronic quenching of OH(A) by water prevents thermalization of the rotational population distribution of OH(A). This means that the observed ro-vibrational OH(A?X) emission band is (at least partially) an image of the formation process and is determined not only by the gas temperature. The formation of negative ions and clusters for larger water concentrations can contribute to the non-equilibrium. The above is demonstrated in RF excited atmospheric pressure glow discharges in He?water mixtures in a parallel metal plate reactor by optical emission spectroscopy. For this particular case a significant overpopulation of high rotational states appears around 1000?ppm H2O in He. The smallest temperature parameter of a non-Boltzmann (two-temperature) distribution fitted to the experimental spectrum of OH(A?X) gives a good representation of the gas temperature. Only the rotational states with the smallest rotational numbers (J ≤ 7) are thermalized and representative for the gas temperature.This publication has 28 references indexed in Scilit:
- Characterization of a direct dc-excited discharge in water by optical emission spectroscopyPlasma Sources Science and Technology, 2009
- Non-thermal plasmas in and in contact with liquidsJournal of Physics D: Applied Physics, 2009
- Room-temperature atmospheric argon plasma jet sustained with submicrosecond high-voltage pulsesApplied Physics Letters, 2007
- Evolution of Discharge Structure in Capacitive Radio-Frequency Atmospheric MicroplasmasPhysical Review Letters, 2006
- Optical measurements of gas temperatures in atmospheric pressure RF cold plasmasSurface and Coatings Technology, 2003
- Optical diagnostics of atmospheric pressure air plasmasPlasma Sources Science and Technology, 2003
- A comparative study of rotational temperatures using diatomic OH, O2 and N2+ molecular spectra emitted from atmospheric plasmasSpectrochimica Acta Part B: Atomic Spectroscopy, 2003
- UV OH spectrum used as a molecular pyrometerJournal of Physics D: Applied Physics, 2000
- A spectroscopic diagnostic method using UV OH band spectrumJournal of Physics D: Applied Physics, 1996
- Calculated rotational transition probabilities for the A−X system of OHJournal of Quantitative Spectroscopy and Radiative Transfer, 1980