DC glow discharge includes of the separate regions, Aston dark space, cathode glow, cathode dark space, negative glow, faraday dark space, positive column, anode dark space.
Plasma regions were distinguish, especially at 300 and 400 volts, where the peaks at 3.3 cm and 3.9 cm represent the negative glow and the cathode glow in addition to areas of darkness between them.
The electrons are emitting through thermo-ionic emission from the cathode, and these electrons gained kinetic energy corresponding to a significant fraction of the cathode from the negative glow
. The collision processes involving excitation in gas molecules, two types such as first kind and second kind collision are occurring.