A study of the emission spectra from discharges on an ice surface

Spectra of the emitted light from an arc formed on an ice surface over a wide range (300-850 nm) were studied using a triggered spectrometer. Detailed analysis of the spectra allowed identifying different atomic lines and molecular bands from the background gases, as well as excited species from polluted ice. Time-resolved spectra were recorded at different stages of arc propagation over an ice surface to gather data on the occurring ionization processes. From comparisons of overall spectra of white and flashover arcs, it was observed that a white arc emits light mostly in the ultraviolet region, whereas a flashover arc emits light mostly in the visible region. It was pointed out that the intensity of some lines, such as copper, increases constantly between the white arc and flashover occurrences. However, the intensity of some lines, such as H_α and H_β and N₂⁺ first negative, increases suddenly during flashover. The possible chemical reactions responsible for emitting observed lines and bands were discussed.