THE CONSTRUCTION AND SPECTROSCOPIC CHARACTERIZATION OF A FAST ELECTRIC-DISCHARGE IN A SUPERSONIC JET

A pulsed electrical discharge instrument has been developed for the efficient production of transient species within a supersonic free-jet. Both the electrical circuitry and electrode design necessary for a short (< 1-mu-s) discharge pulse, enabling laser induced fluorescence experiments to be carried out to within 5-mu-s of the discharge, are described. Laser-induced fluorescence has been used both to identify transient species created and to investigate the optimum conditions for their production. In particular two prototype transient species OH and N2+ were observed and their relative densities and characteristic Boltzmann rotational temperatures determined under various experimental conditions. The relative density of cold transient species was found to be highly dependent upon discharge timing, electrode to orifice distance and on laser timing. The instrument which is of simple construction and low cost is shown to produce a variety of transient species including ions, radicals, metastables and open-shell clusters.