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\section{Introduction}  The Franck-Hertz experiment demonstrates the quantum behavior of atoms and provides outstanding evidence that the transfer of energy to electrons should always be discrete, regardless of the mechanism of energy transfer. Furthermore it affirms the theory that all atoms consist of discrete stationary energy levels. Franck and Hertz focused their experiment on energy transfer by low-energy electron bombardment, so no other methods of energy transfer were included in the particular experiment. It was theorized that if the atoms being bombarded do not become ionized, then almost the entire energy of the bombarding electron will be transferred to the atomic system. In this version of the experiment only the energy required to excite the first energy levels were determined, although it is possible to find the excitation energy for levels of a higher order.   \parA A  typical arrangement of the Franck-Hertz experiment consists of an electron-emitting filament and a means of accelerating electrons to a variable potential. These accelerated electrons then bombarded atoms of the element, which are usually in a gaseous state. In order to detect the excitation of atoms, the current of electron beam can be observed. Specifically, it is expected that if the electrons have been accelerated to a potential that is equal to the discrete energy of the first excited level, some of atoms of the element will become excited, the bombarding electrons will lose most of their energy, and the collision is inelastic. If a small retarding potential exists before the anode, which is used to collect remaining electrons, electrons that have lost most of their energy will not be able to overcome it, and thus will not reach the region of collection. This should correspond to a decrease in current of the electron beam. \parIn In  order to create these particular circumstances in the experimental arrangement two grids are placed between an electron-emitting cathode (filament) and an anode used for electron collection. The beam is accelerated between the cathode and grid 1 ($G_{1}$), then bombards atoms of the element between grid 1 and grid 2 ($G_{2}$). A retarding voltage between grid 2 and the anode prevents electrons that have lost most of their energy from reaching the anode. When the atoms in the vapor are excited to their first energy level, a decrease in the electron current is observed, as is true for when the atoms are excited to energy levels of higher values. These dips are located on a rising background curve. Dips are not perfectly sharp, due to the of the lifetime of each excited state, and due to the distribution of velocities for emitted electrons. Though it was previously thought that these dips were equidistant to one another, more recent studies have shown that the distance between successive points increases linearly. Plots of the linearly increasing distances between these points were analyzed in order to determine excitation energy for the lowest state for all three elements. \subsection{Experiment}