deletions | additions       diff --git a/The_discrete_energy_levels_can__.tex b/The_discrete_energy_levels_can__.tex  index f11706f..55969ff 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 16.6eV, 16.62eV,  and the second excitation energy level is 18.38eV. 18.38eV.For Ar, the four sub levels within the first energy level are 11.55eV, 11.62eV, 11.72eV and 11.83eV respectively.  More stuff to discuss...  \begin{itemize}  %\item mean free path + equations