, Volume 76, Issue 7, pp 775-785
Date: 24 Jun 2003

Two-photon polarization spectroscopy applied for quantitative measurements of atomic hydrogen in atmospheric pressure flames

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Abstract

Two-photon – polarization spectroscopy has been applied for the first time to determine absolute number densities and kinetic temperatures of atomic hydrogen via the 1S–2Stransition in flames at atmospheric pressure. This sensitive laser spectroscopic technique, so far mainly developed and applied for quantitative plasma diagnostics, is also well suited for real combustion processes, because the signal is directly related to the two-photon absorption itself and therefore not limited by quenching or photo-ionization. It can be applied with high spatial and temporal resolution in a wide range of pressure and temperature. Furthermore, a well-established calibration procedure allows for a precise determination of the absolute ground-state density of atomic hydrogen. The measurements also demonstrate that a certain potential of this method comes especially into its own in conjunction with laser radiation of highest spectral quality, i.e. pulsed single-longitudinal mode UV radiation.

PACS

52.70.-m; 32.80.Wr; 39.30.+w; 42.65.-k; 82.90.+j