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P: Plasmaphysik

P 10: Theory and Plasma Diagnostic (Poster Session)

P 10.21: Poster

Wednesday, April 4, 2001, 12:30–15:00, AT2

TALIF calibration with noble gases for quantitative atomic density measurements — •K. Niemi, V. Schulz-von der Gathen, and H.F. Döbele — Universität Essen, Institut für Laser- und Plasmaphysik, Universitätsstr.5, 45117 Essen, Germany

In order to obtain absolute atomic ground state densities with two-photon absorption laser induced fluorescence spectroscopy (TALIF) a reliable calibration technique and the consideration of collisional quenching effects on the induced population are required.

A comparative measurement with a noble gas having a two-photon resonance spectrally close to the atomic transition can be used as a calibration that needs neither additional diagnostics nor major modification of the TALIF set-up. Suitable transitions exist in krypton and xenon for the two-photon excitation of atomic hydrogen at 205.1 nm, nitrogen at 206.6 nm and oxygen at 225.5 nm. We investigated these excitations by TALIF in order to determine the atomic data required for this calibration. The radiative lifetimes of the excited states and the quenching coefficients for collisions with several important species were obtained from time resolved measurements. The relevant ratios of the two-photon excitation cross sections were determined from comparative measurements with known densities. The atomic reference densities were generated in a flow tube reactor with the aid of titration methods.