The remaining electrons reach the anode, building up a large negative charge. This effect, in which a single electron causes many electrons to flow between the electrodes, is called electrical discharge. Click on the picture above. Now let's look at the luminescence caused by discharge in a little more detail. Air molecules consist of atoms such as nitrogen and oxygen.
Atoms contain a nucleus, around which a field of electrons circles.
As collision with the electrons emitted from the cathode intensifies, the electrons in the atoms gather energy from the collisions, jumping into higher orbits around the nucleus and ultimately breaking free. However, these electrons raised into higher orbits are in a less stable state than their previous orbits, and soon return to their original orbits in search of stability.