Abstract

One of the most important, and difficult to measure, parameters of laboratory discharges in molecular gases is the gas translational temperature. We measure, with excellent spatial and temporal resolution, the velocity distribution of oxygen ground-state atoms in plasmas from the Doppler broadening of their laser excitation spectra. The method is based on the well-known Two-Photon Absorption Laser-induced Fluorescence (TALIF) technique, but uses a specially-built pulsed tunable ultraviolet laser with very narrow bandwidth which allows the Doppler profiles to be measured with high precision. This laser consists of a pulsed Nd:YAG-pumped Ti:Sapphire ring cavity which is injection-seeded by a singlemode cw Diode laser. The single-mode infrared output pulses are frequency quadrupled by two non-linear crystals to reach the necessary UV wavelength (226 nm, 0.2 mJ) for TALIF excitation.

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