James Franck

James Franck (1882–1964) was a German-American physicist who shared the 1925 Nobel Prize in Physics for experiments demonstrating quantized atomic energy levels.

Gustav Hertz: A German physicist who shared the 1925 Nobel Prize with Franck for experiments on electron collisions with atoms. Franck and Hertz jointly conducted the experiments that revealed discrete atomic excitation energies.
Franck–Hertz experiment: An experiment in which electrons collide with atoms, revealing discrete atomic excitation energies through changes in electron current. This is the experimental method Franck and Hertz used to demonstrate quantized atomic energy transfer.
University of Berlin: A German university in Berlin, founded in 1810 and now named Humboldt University of Berlin. Franck studied physics there and completed his doctorate under Emil Warburg.
Quantum mechanics: The physical theory describing matter and energy through quantized states and probabilistic laws. The experiment supplied direct evidence for the quantization central to the emerging theory.
Niels Bohr: A Danish physicist whose atomic model proposed electrons occupy discrete energy levels. Bohr’s model predicted the discrete energy transfers Franck and Hertz measured.
Electron impact excitation: The transfer of energy from a colliding electron to an atom or molecule, leaving it in an excited state. Franck and Hertz inferred atomic excitation from electrons losing specific amounts of energy in collisions.
Emil Warburg: A German physicist known for research on gas discharges, radiation, and the kinetic theory of gases. Warburg supervised Franck’s doctoral research on the motion of ions in gases.
Manhattan Project: The United States-led wartime program that developed the first nuclear weapons. Franck worked on the project’s chemistry at the University of Chicago during World War II.
Max Born: A German physicist who helped establish quantum mechanics and directed Franck’s institute in Göttingen. Born and Franck worked together in Göttingen during the development of quantum physics.
Atomic energy level: A permitted energy value of an atom, determined by its quantum state. The experiment’s discrete energy losses corresponded to transitions between atomic energy levels.

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