James Franck and Gustav Ludwig Hertz measured the transfer of kinetic energy from free electrons into atomic excitation. In Mercury vapor, the collected electric current changes repeatedly as the accelerating voltage rises. Below an excitation threshold, an electron cannot excite the relevant atomic quantum state; above it, an inelastic collision can remove a characteristic energy. Repeated acceleration and energy loss produce the successive features, linking the Franck-Hertz experiment to quantized atomic structure.[ref]
Über Zusammenstöße zwischen Elektronen und den Molekülen des Quecksilberdampfes und die Ionisierungsspannung desselben by James Franck and Gustav Ludwig Hertz. Mercury-vapor electron-impact measurements
[ref]Transformations of Kinetic Energy of Free Electrons into Excitation Energy of Atoms by Impacts by James Franck. Nobel lecture: interpretation of excitation-energy transfer
Portrait of James Franck
. Source. - Nobel Lectures, Physics 1922–1941 Transformations of Kinetic Energy of Free Electrons into Excitation Energy of Atoms by Impacts by James Franck
- Über Zusammenstöße zwischen Elektronen und den Molekülen des Quecksilberdampfes und die Ionisierungsspannung desselben by James Franck and Gustav Ludwig Hertz
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James Franck (1882–1964) was a German physicist who is best known for his work in atomic and molecular physics. He was awarded the Nobel Prize in Physics in 1925, alongside Gustav Hertz, for their experiments demonstrating the behavior of electrons in atoms, which contributed significantly to the understanding of quantum mechanics. Franck's most notable contribution was the Franck-Hertz experiment, which provided evidence for the quantized nature of atomic energy levels.