Detection of atomic hydrogen in flames using picosecond two-color two-photon-resonant six-wave-mixing spectroscopy
We report an investigation of two-color six-wave-mixing spectroscopy techniquesusing picosecond lasers for the detection of atomic hydrogen in anatmospheric-pressure hydrogen-air flame. An ultraviolet laser at243 nm was two-photon-resonant and a visible probelaser at 656 nm was resonant with H{alpha} transitions (n=3 (leftarrow) n=2). The signal dependence on the polarization of the pump laser was investigated for a two-beam polarization-spectroscopy experimental configuration and for a four-beam grating configuration. A direct comparison of the absolute signal and backgroundl evels in the two experimental geometries demonstrated a significant advantage to using the four-beam grating geometry over the simpler two-beam configuration. Picosecond laser pulses provided sufficient time resolution to investigate hydrogen collisions in the atmospheric-pressure flame. Time-resolved two-color laser-induced fluorescence was used to measure an n=2 population lifetime of 110 ps, and time-resolved two-color six-wave-mixing spectroscopy was used to measure a coherence lifetime of 76 ps. Based on the collisional time scale, we expect that the six-wave-mixing signal dependence on collisions is significantly reduced with picosecond laser pulses when compared to laser pulse durations on the nanosecond time scale.
- OSTI ID:
- 20929754
- Journal Information:
- Applied Optics, Journal Name: Applied Optics Journal Issue: 19 Vol. 46; ISSN 0003-6935; ISSN APOPAI
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND TECHNOLOGY
71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
AIR
ATMOSPHERIC PRESSURE
ATOM COLLISIONS
COLOR
COMBUSTION
CONFIGURATION
DIFFRACTION GRATINGS
FLAMES
FLUORESCENCE
GEOMETRY
HYDROGEN
LASERS
NONLINEAR OPTICS
PHOTONS
POLARIZATION
SIGNALS
SPECTROSCOPY
TIME RESOLUTION
ULTRAVIOLET RADIATION
VISIBLE RADIATION