Detection of atomic hydrogen in flames using picosecond two-color two-photon-resonant six-wave-mixing spectroscopy.

摘要: We report an investigation of two-color six-wave-mixing spectroscopy techniques using picosecond lasers for the detection atomic hydrogen in an atmospheric-pressure hydrogen-air flame. An ultraviolet laser at 243 nm was two-photon-resonant with the 2S½ ←← 1S½ transition, and a visible probe laser at 656 was resonant with Hα transitions (n=3 ← n=2). The signal dependence on polarization pump investigated two- beam polarization-spectroscopy experimental configuration four- beam grating configuration. A direct comparison absolute signal background levels two geometries demonstrated significant advantage to using four-beam geometry over simpler two-beam configuration. Picosecond pulses provided sufficient time resolution investigate hydrogen collisions atmospheric-pressure Time-resolved two-color laser-induced fluorescence used measure n=2 population lifetime 110 ps, time-resolved spectroscopy was coherence lifetime 76 ps. Based on collisional scale, we expect that dependence on is significantly reduced when compared pulse durations nanosecond scale.