Franck hertz Experiment-Ionization vs Excitation

[realgenob]

Franck hertz Experiment--Ionization vs Excitation

Homework Statement

We performed the Franck-Hertz experiment with neon gas. As we raised the accelerating voltage, the electrons gained enough energy to raise the energy of the neon through inelastic collisions. Those electrons lose some energy and and can't reach the cathode due to the retarding voltage which in turn causing the voltage to drop. When the gas returns to a lower state, the collisions with the electrons are again elastic and the electrons reach the cathode, restoring the higher current. I understand that process, however, I have an analysis question that ask "Why doesn't the gas ionize when the accelerating voltage is raised beyond the ionizing potential of neon.

Homework Equations

The Attempt at a Solution

 

[jbsteele]

The main reason why the gas doesn't ionize when the accelerating voltage is raised beyond the ionization potential of neon is because the electrons gain enough energy to raise the energy of the neon through inelastic collisions, but not enough energy to fully ionize the gas. Because of this, the electrons are able to lose some energy and be unable to reach the cathode due to the retarding voltage which in turn causes the voltage to drop. When the gas returns to a lower state, the collisions with the electrons are again elastic and the electrons reach the cathode, restoring the higher current.