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Proceedings Paper

Measurement of quenching coefficients and development of calibration methods for quantitative spectroscopy of plasmas at elevated pressures
Author(s): Anne Francis; Timo Gans; Kari Niemi; U. Czarnetzki; Volker Schulz-von der Gathen; H. F. Dobele
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Paper Abstract

Measurements of collisional de-excitation (quenching) coefficients required for the interpretation of emission and fluorescence spectroscopic measurements are reported. Particular attention is turned on argon transitions which are of interest for actinometric determinations of atomic ground state populations and on fluorescence lines originating from excited atoms and noble gases in connection with two-photon excitation (TALIF) of atomic radicals. A novel method is described which allows to infer quenching coefficients for collisions with molecular hydrogen of noble gas states in the energy range up to 24 eV. The excitation is performed in these experiments by collisions of energetic electrons in the sheath of an RF excited hydrogen plasma during the field reversal phase which lasts about 10 ns. We describe in addition a calibration method -including quenching effectsf o-r the determination by TALIF of absolute atomic radical densities of hydrogen, nitrogen and oxygen using two-photon resonances in noble gases close by the resonances of the species mentioned. The paper closes with first ideas on a novel technique to bypass quenching effects in TALIF by introducing an additional, controllable loss by photoionization that will allow quenching-free determination of absolute atomic densities with prevalent nanosecond laser systems in situations where collisional de-excitation dominates over spontaneous emission.

Paper Details

Date Published: 19 March 2002
PDF: 12 pages
Proc. SPIE 4460, Selected Research Papers on Spectroscopy of Nonequilibrium Plasma at Elevated Pressures, (19 March 2002); doi: 10.1117/12.459391
Show Author Affiliations
Anne Francis, Univ. Gesamthochschule Essen (Germany)
Timo Gans, Univ. Gesamthochschule Essen (Germany)
Kari Niemi, Univ. Gesamthochschule Essen (Germany)
U. Czarnetzki, Univ. Gesamthochschule Essen (Germany)
Volker Schulz-von der Gathen, Univ. Gesamthochschule Essen (Germany)
H. F. Dobele, Univ. Gesamthochschule Essen (Germany)

Published in SPIE Proceedings Vol. 4460:
Selected Research Papers on Spectroscopy of Nonequilibrium Plasma at Elevated Pressures
Vladimir N. Ochkin, Editor(s)

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