Q:

How does a high voltage produce ions

I was reading about gas discharge tubes and it said that when a high voltage is applied between the cathode and anode, electrons get pulled off the gas atoms. My question is how does this happen simply because of a high voltage? I thought you needed electrons to collide with the gas atoms and knock off electrons, but I never heard about them being pulled off gas atoms by a high voltage. Can someone explain how this works?
Thanks

A:

You're correct that it's not the high voltage itself which ionizes the atoms, but rather the free electrons accelerated by this electric field.
In any system at finite temperature, there is a non-zero probability for some atoms to be ionized at any given time. Applying a strong electric field causes the free electrons to accelerate. Collisions with bound atoms then result in electrons being ejected from their orbitals, which are accelerated by the field and go on to ionize yet more atoms. The resulting electron avalanche can lead to near-complete ionization of the entire gas discharge.

