| Affiliation: | (1) School of Mechanical Engineering, Purdue University, West Lafayette, IN 47907, USA;(2) Department of Physics and Engineering, Washington &; Lee University, Lexington, VA 24450, USA;(3) Innovative Scientific Solutions, Inc., 2766 Indian Ripple Road, Dayton, OH 45440, USA;(4) Propulsion Directorate, Air Force Research Laboratory, Wright-Patterson AFB, OH 45433, USA; |
| 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 1 S–2 Stransition 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. |
