COMPARISON OF FEMTOSECOND AND NANOSECOND TWO PHOTON ABSORPTION LASER INDUCED FLUORESCENCE (TALIF) OF ATOMIC OXYGEN IN ATMOSPHERIC PRESSURE PLASMAS
Technical Report,29 Nov 2012,22 Aug 2016
Electrical Systems Branch, Power and Control Division (AFRL/RQQE) Wright-Patterson Air Force Base United States
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Absolute number densities of atomic species produced by nanosecond duration, repetitively pulsed electric discharges are measured by two-photon absorption laser-induced fluorescence TALIF. Unique to this work is the development of femtosecond-laser-based TALIF fs-TALIF. Fs-TALIF offers a number of advantages compared to more conventional ns-pulse-duration laser systems, including better accuracy of direct quenching measurements in highly collisional environments, significantly reduced photolytic interference including photo-dissociation and photo-ionization, higher signal and increased laser-pulse bandwidth, the ability to collect two-dimensional images of atomic species number densities with high spatial resolution, and much higher laser repetition rates allowing for more efficient and accurate measurements of atomic species number densities. In order to fully quantify these advantages, atomic oxygen TALIF signals are collected from an atmospheric-pressure plasma jet APPJ for both nanosecond- and femtosecond-duration laser excitation pulses.