New Features in Frank-Hertz Experiment with Argon: Experiment and Monte Carlo Simulation

In this work, a homemade apparatus was built to perform the Frank-Hertz experiment with argon. The lowest energy state and the higher energy state of argon can be excited by the Frank-Hertz experiment. The excitation energies of the argon atom are measured by using the setup. The obtained higher excitation energy of argon atoms is 13.73 ± 0.28 eV, for the mixture of higher energy states 3s23p53d and 3s23p54p. A plate capacitor model was constructed to simulate the inelastic collisions between electron and argon atoms using the Monte Carlo method. The simulated current curve and electron energy distribution agrees with that of Frank-Hertz experiments, especially the features of higher excited state. The Monte Carlo simulation indicate the deformed electron energy distribution result from the change in excitation proportion of energy levels during the collisions of electrons and argon atoms. Moreover, the new features in Frank-Hertz curve are ascribed to the higher excitation states of argon atoms. The experimental setup has been applied to undergraduate physics experiment teaching in college. Students can perform the Frank-Hertz curve measurement not only the lowest excited state, but also the higher excited states of argon. In addition, students can do the Monte Carlo simulations for the experimental Frank-Hertz curves and gain a better understanding of electron-argon atom collisions in the experiment. The new designed experiment will make students more familiar with the quantum behavior in atomic physics and quantum mechanics course.