These experiments measure two phenomena encountered in collisions between electrons and atoms: quantized excitation due to inelastic scattering, and ionization. The excitation potential and ionization potential of the mercury atom are determined from measurements of the critical accelerating potentials at which electrons lose energy by inelastic scattering in mercury vapor.
Franck-Hertz Experiment References
Bohm, David. "Square Potential Solutions." In Quantum Theory. Upper Saddle River, NJ: Prentice Hall, 1951, pp. 229-263.
Bleuler, Ernst, and George J. Goldsmith. "Charged Particle Spectra." In Experimental Nucleonics. New York, NY: Rinehart, 1952, pp. 342-346.
Schiff, Leonard I. "Ramsauer-Townsend Effect." In Quantum Mechanics. 3rd ed. New York, NY: McGraw-Hill, 1968, pp. 108-110.
Harnwell, Gaylord P., and J. J. Livinwood. "Experiments on Excitation Potentials," and "Experiments in Ionization Potentials." In Experimental Atomic Physics. Huntington, NY: R. E. Krieger, 1978, pp. 314-320. ISBN: 9780882756004.
Rapior, G., K. Sengstock, and V. Baeva. "New Features of the Franck-Hertz Experiment." American Journal of Physics 74 (2006): 423-428.
Ramsauer-Townsend Effect Experiment References
Bohm, David. "Ramsauer-Townsend." In Quantum Theory. Upper Saddle River, NJ: Prentice Hall, 1951, pp. 564-573.
Kukolich, Stephen G. "Demonstration of the Ramsauer-Townsend Effect in a Xenon Thyratron." American Journal of Physics 36, no. 8 (1968): 701-703.