APPLICATION OF THE STARK EFFECT IN NAK MOLECULE TO THE DETERMINATION OF THE LOCAL ELECTRIC FIELD IN PLASMAS.

Electric-field-induced mixing between e and f 2z-doublet states of an NaK (B**1 II) molecule was used to determine the amplitude of the local electric field inside a discharge. This nonperturbative technique is based on the laser-induced fluorescence spectrocopy of NaK (B--X) transition with a tunable continuous-wave laser. Preliminary results clearly show the ability of the NaK molecule to be used as a highly sensitive and adjustable probe for electric-field measurements in plasmas in which sodium and potassium are naturally present or could be introduced in small quantity. The strong polarization dependence of the observed signal indicates that it could also be possible to deduce the direction of the electric-field vector. The spatial resolution of this technique results from the finite diameter of the laser beam and/or the monochromator entrance slit width at which the image of the laser excited volume is formed. Electric fields of a few V/cm up to several kV/cm can be measured with a spatial resolution of 0. 1 mm.