Work functions for a HV cathode in nonpolar liquids

When negative HV is applied to a needle of small radius of curvature (r_p<0.2 μm) in nonpolar liquids, a detectable field emission current (I>×10^-12 A) is observed above a voltage U_FN, the Fowler-Nordheim law. For larger point radii, only a regular current pulse regime is detected above a threshold voltage U_s (Trichel regime). Analysis of these voltages U_s and U_FN as a function of conduction band energy V₀ of different liquids, shows that the apparent work function for high electric field strengths in liquids is lower than the one without applied field (2.1 compared to 4.5 eV for a tungsten cathode). This difference can be explained if one assumes the existence of a plasma-like layer around the HV cathode