Streamer Branching and Spectroscopic Characteristics of Surface Discharge on Water Under Different Pulsed Voltages

Complexity of branching pattern and OH production of water surface discharges was investigated by comparing nanosecond water surface discharge (NWSD) and microsecond water surface discharges (MWSDs) that were defined as NWSD and MWSD, respectively. Experimental and analyzed results between NWSD and MWSD under comparable maximum discharge length l d are summarized as follows: 1) NWSD showed the greatest complexity of branching pattern by fractal analysis; 2) electron density of NWSD was approximately two times greater than MWSD and both orders were 10 -17 cm -3 ; 3) emission intensity of OH (A-X) from MWSD was greater than NWSD; 4) rotational temperature of NWSD was almost constant around 1000 K irrespective of l d and rotational temperature of MWSD increased with increasing l d ranging from 2000 to 4000 K. It was found that the complexity of discharge pattern on water may be affected by the field intensity at water/air boundary. OH production was presumed to be caused by thermal dissociation in this experimental condition.