EPJ D Colloquium - One Hundred Years of the Franck-Hertz Experiment

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Published on 21 July 2014

The seminal 1914 experiment of James Franck and Gustav Hertz provided a graphic demonstration of the quantisation properties of atoms, and thereby laid the foundations of modern atomic physics. This EPJ D colloquium revisits the experiment on the occasion of its Centenary and compares the traditional and modern interpretations, as well as highlighting the link between microscopic processes, which are governed by the laws of quantum mechanics, and macroscopic phenomena, as observed in the laboratory.

The aim of this review is to place the physics underlying the operation of the Franck-Hertz experiment within the context of contemporary gaseous electronics, and to that end a result dating back even further, namely the 1872 kinetic equation of Ludwig Boltzmann, is revisited. It is also shown how the Franck-Hertz experiment can be modelled using fluid equations and Monte-Carlo simulations, and finally how the non-local effects, resonances and striations observed in plasmas have much in common with the electron physics in the drift region of the Franck-Hertz experiment.