deletions | additions       diff --git a/The_discrete_energy_levels_can__.tex b/The_discrete_energy_levels_can__.tex  index 88f8722..d5251e6 100644  --- a/The_discrete_energy_levels_can__.tex  +++ b/The_discrete_energy_levels_can__.tex 
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[The discrete energy levels can be explained by elastic and inelastic collisions between the electrons and the neon or argon atoms. When the accelerating voltage applied to the cathode is above a certain point, the Franck-Hertz experiment found that there are no longer only elastic collisions. The inelastic collisions occur once the electron has enough energy to excite the atom.] <-- should i remove?  The distance the electron travels before colliding with an atom and exciting it is called the mean free path.  More stuff to discuss??  \begin{itemize}  \item mean free path