7B30.12 - Franck-Hertz : Xenon

See procedure.
See procedure.
Code Number:
Demo Title:
Franck-Hertz : Xenon
Critical Potential in a Gas
Area of Study:
Modern Physics
Franck - Hertz Xenon Tube Unit, 0 to 20 VDC Power Supply, 2 - Variacs, 2 - 6 volt Transformers, Volt and Amp Meters, Oscilloscope.

This version of the Franck - Hertz experiment is built around the 2D21 electron tube that has an appreciable amount of xenon gas present.  Since we like to show our peak on an oscilloscope instead of plotting it out, our hookup is a little different than that described in the instruction booklet in the files. We impress a 60 cycle, three volt ripple on the 0 to 12 VDC side of the circuit. Run the DC power supply at about 4 to 5 volts. Usually the ripple can be held to around 2 volts when everything stabilizes. The meter amplifier switch must be to Experiment 1 on the Franck - Hertz unit. Some tweaking of the power supply voltages and the control knobs on the Franck - Hertz unit will probably be necessary to obtain the best trace. Only one peak will be obtained with this unit.  

  • Harry F. Meiners, "Ionization Potential of Xenon", AJP, Vol. 33, # 5, May 1965, p.17.
  • W. Bolton, "Energy Levels", Book 3 - Atomic Physics, Physics Experiments and Projects, 1968, p. 27-28. 

Disclaimer: These demonstrations are provided only for illustrative use by persons affiliated with The University of Iowa and only under the direction of a trained instructor or physicist.  The University of Iowa is not responsible for demonstrations performed by those using their own equipment or who choose to use this reference material for their own purpose.  The demonstrations included here are within the public domain and can be found in materials contained in libraries, bookstores, and through electronic sources.  Performing all or any portion of any of these demonstrations, with or without revisions not depicted here entails inherent risks.  These risks include, without limitation, bodily injury (and possibly death), including risks to health that may be temporary or permanent and that may exacerbate a pre-existing medical condition; and property loss or damage.  Anyone performing any part of these demonstrations, even with revisions, knowingly and voluntarily assumes all risks associated with them.