When a condensor is discharged between two electrodes in a thin Layer of liquid, a light flash is produced. The light emission is detected with a fast silicon detector filtered for red, green and blue light. The spark discharge and the shock waves in the liquid layer are photographed with X-ray flashes. The energy transfer to the gas plasma is much higher for a second or third discharge which follows the first discharge after some microseconds, if it is a discharge into the spark induced gas plasma and not in the liquid. The expansion of the gas plasma has been studied therefore in detail. A simple arrangement of two condensors and a coil makes it possible to produce flash sequences. The spark was produced in different organic liquids and H2O.
"Light Emission Of Spark Discharges In Liquids", Proc. SPIE 0312, 1st European Conf on Cineradiography with Photons or Particles, (9 August 1983); doi: 10.1117/12.932922; https://doi.org/10.1117/12.932922