Prebreakdown phenomena in hydrocarbon liquids

Prebreakdown light emission, photocurrent, conduction current and density change (streamer) are measured simultaneously in hydrocarbon liquids. Similar phenomena are observed in saturated n-hexane and cyclohexane. The shapes of light emission and streamer are only bush-type for a negative point, but both bush-type and tree-type for a positive one. However, a great difference is observed in unsaturated 1-hexane and benzene. In 1-hexane, there is only bush-type streamers for a negative point, and tree-type for a positive one. In benzene, there are both bush-type and tree-type streamers for a negative point, but only a radial-type for a positive one.