The color of the glow of the discharge plasma at electrodes made of various metals is associated with excitation certain energy levels of particles in the vapors of these metals. So, when using electrodes made of aluminum, steel and copper, we observed the glow of red, blue and green colors, respectively. The different colors of the discharge when changing the material of the electrodes are determined not by the spark or arc stages, but by bright spots on the electrodes, which are formed due to the explosive emission of electrons [Mesyats, G.A. Ecton mechanism of the vacuum arc cathode spot. IEEE transactions on plasma science, 1995, 23(6), pp. 879-883. (DOI: 10.1109/27.476469)]. These areas in the photographs have a bright white color (see, for example, the photographs in Figures 3, 6, 7). In spark or arc discharge, as well as in bright spots the electrodes are locally heated to a high temperature, which leads to the evaporation of the electrode material. High-temperature zones on the electrodes also supply micro- and nanoparticles into a discharge gap. However, emission of individual particles is determined by their temperature, it corresponds to the Planck radiation and is broadband. We note once again that in this work, to obtain metal vapors, as well as metal nano- and microparticles, a pulsed nanosecond discharge in a non-uniform electric field was used.
One can agree with the influence of the particle size on the track size, but how can an increase in the particle charge affect the track glow?