• Measure the collector current IR as a function of the accelerating voltage UA.
• Compare the positions of the current maxima with the known critical potentials of the helium atom.
• Identify the doublet structure in the term scheme of helium (ortho and para helium).
Experiment description: ..
The expression “critical potential” is a general name for all the excitation and ionisation energies in the electron shells of an atom. The corresponding electronic states can be excited in various ways, for example by inelastic collisions with electrons. If the kinetic energy of the electron corresponds to a critical potential, the electron can lose all its kinetic energy in an inelastic collision. An experiment setup originally designed by Gustav Hertz is used here to determine critical potentials.
![Experiment: Critical Potentials (115 V, 50/60 Hz), 8000715 [UE5020500-115], Atomic shells](/imagelibrary/UE5020500-115/UE5020500-115_01_Experiment-Critical-Potentials-115-V-5060-Hz.jpg)
![Experiment: Critical Potentials (115 V, 50/60 Hz), 8000715 [UE5020500-115], Atomic shells](/thumblibrary/UE5020500-115/UE5020500-115_01_1200_1200_Experiment-Critical-Potentials-115-V-5060-Hz.jpg)
