Time-resolved absolute OH density of a nanosecond pulsed discharge in atmospheric pressure He–H₂O: absolute calibration, collisional quenching and the importance of charged species in OH production

Abstract

Link to publication Citation for published version (APA):Verreycken, T., Sadeghi, N., & Bruggeman, P. J. (2014). Time-resolved absolute OH density of a nanosecond pulsed discharge in atmospheric pressure He-H2O : absolute calibration, collisional quenching and the importance of charged species in OH production. Plasma Sources Science and Technology, 23(4), 45005-1/9. DOI: 10.1088/0963-0252/23/4/045005 General rightsCopyright and moral rights for the publications made accessible in the public portal are retained by the authors and/or other copyright owners and it is a condition of accessing publications that users recognise and abide by the legal requirements associated with these rights.• Users may download and print one copy of any publication from the public portal for the purpose of private study or research.• You may not further distribute the material or use it for any profit-making activity or commercial gain • You may freely distribute the URL identifying the publication in the public portal ? Take down policyIf you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediately and investigate your claim. AbstractThe time-resolved OH density in a nanosecond pulsed filamentary discharge in an atmospheric pressure He-H 2 O(0.05%) mixture is measured using laser induced fluorescence. The lifetime of the excited OH(A) state is found to be strongly time dependent during the plasma pulse, with the shortest decay time occurring at the moment the plasma is switched off. The measured LIF intensity is corrected for this time-resolved quenching and calibrated using Rayleigh scattering. Time-resolved electron density (n max e = (7.6 ± 0.8) × 10 21 m −3 ), He ( 3 S 1 ) metastable density (He max m = (1.6 ± 0.3) × 10 20 m −3 ), gas temperature (T max g = (350 ± 60) K) and optical emission are presented and used in the interpretation of the observed time dependence of the OH density. Based on these experimental data, it is shown that for the present discharge conditions, OH is mainly produced by charge transfer reactions to water followed by dissociative recombination of the water ion. In addition, two often encountered issues with the calibration of OH LIF are highlighted with an example.

Corrigendum on ‘OH Density Measurements by Time-Resolved Broad Band Absorption Spectroscopy in a He-H2 O Dielectric Barrier Discharge With Small O2 Addition’

“…Note that this is also true for the results of Ref . as the same authors have first pointed out in Ref …”

“…. Following the observations made in Ref ,. we acknowledge that the calculation of OH density from absorption spectra is affected by a factor of two error.…”

“…[3] , we acknowledge that the calculation of OH density from absorption spectra is affected by a factor of two error. Such a mistake arises from the neglect of the L-doubling splitting of the ground state rotational levels.…”

Chemical kinetics in an atmospheric pressure helium plasma containing humidity

“…Laser Induced Fluorescence (LIF) and Two-photon Absorption LIF (TALIF) have been previously used to detect species such as O and OH produced from water vapor. 31 – 34 However, in order to accurately predict the effect of quenching using these techniques at atmospheric pressure, the densities of all potential quenching particles are needed. This is increasingly challenging in complex gas mixtures and in regions with gradual gas mixing, like the plasma effluent.…”

Analysis of hydroxyl radical formation in a gas‐liquid electrical discharge plasma reactor utilizing liquid and gaseous radical scavengers

“…For example, optical emissions spectroscopy (OES), has been used to identify and quantify the • OH bands from water dissociation in a wide range of discharges including those directly inside the liquid phase as well as those in the gas phase over a liquid and in humid gases . In addition, laser induced fluorescence (LIF), has been used to quantify the density of • OH in the vapor phases of a number of plasma processes . A recent review and roadmap of plasma‐liquid interactions summarizes many of the diagnostic tools used for analyzing plasma chemistry and physics and other recent work in the field of plasma medicine has addressed specifically • OH production .…”