Laser-Based Ignition of H2/O2 and D2/O2 Premixed Gases Near 243 nm: The First Report of a Deuterium Isotope Wavelength Effect in Laser Ignition
Final rept. Jan-Dec 1990
ARMY BALLISTIC RESEARCH LAB ABERDEEN PROVING GROUND MD
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We investigated the use of a tunable laser system which operates in the ultraviolet uv to ignite premixed reactive gaseous flows of H2O2 and D2 O2 at atmospheric pressure. The amount of incident laser energy ILE required to ignite the premixed flows as a function of laser excitation wavelength show two distinct minima. The spectral position of these minima correspond exactly to the location of the resonance, two-photon exictation wavelengths of atomic hydrogen and deuterium at 243.07 and 243.00 nm respectively. The relative spacing between these minima at the energy level of the 1S-2S two-photon excited transition is 22cm which is in excellent agreement with the known value for H-D deuterium isotope shift 22.4cm. We believe that this is both the first report of a sensitive wavelength dependence on the laser energy required to ignite these mixtures through resonant multiphoton excitation of H and D atoms produced from H2 and D2 photolysis and the first report of a deuterium isotope-wavelength-effect in laser ignition. Measurement of the ILE required for ignition vs. equivalence ratio phi shows that the most efficient ignition occurred with approx. 0.55 mJ ILE at phi0.7 in the fuel lean region.
- Radiation and Nuclear Chemistry
- Combustion and Ignition