deletions | additions       diff --git a/The_discrete_energy_levels_can__.tex b/The_discrete_energy_levels_can__.tex  index d34ddfb..f11706f 100644  --- a/The_discrete_energy_levels_can__.tex  +++ b/The_discrete_energy_levels_can__.tex 
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where $\lambda$ is the mean free path, $L$ is the distance between accelerating grid and control grid, $\Delta E(n)$ is the spacing between two minima in Franck Hertz experiment, $n$ is the minimum order and $E_{a}$ is the lowest excitation energy.  According to the NIST Atomic Spectra Database, the first excitation energy of Ne I is 16.619eV, 16.6eV,  and the second excitation energy level is 18.38eV.  More stuff to discuss...  \begin{itemize}