When the external power circuit is connected, the transformer output generates a high voltage of several thousand or even tens of thousands of volts. When this high voltage is applied to the electrodes at both ends of the neon tube, the charged particles inside the tube are accelerated in the high-voltage electric field and fly towards the electrodes, generating a large number of electrons. These excited electrons are accelerated in the high-voltage electric field and collide with gas atoms inside the tube.
When the energy of these electrons colliding with the free gas atoms is large enough, the gas atoms are ionized into positive ions and electrons; this is the phenomenon of gas ionization. The excess energy from the collisions between charged particles and gas atoms is emitted in the form of photons, thus completing the entire process of the neon light illuminating the tube.
