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Incoming links: The discovery of electron waves by Clinton J. Davisson
Davisson–Germer experiment 2026-10-14
The Davisson–Germer experiment turned elastic scattering from nickel into evidence for a matter wave. The search became a deliberate wave test in 1926, with diffraction beams found early in 1927. The earlier crystal investigation had begun in 1925; the de Broglie wavelength proposal was already present in the 1924 thesis.[ref]
A heated tungsten ribbon supplied Electrons; gun apertures selected a narrow beam. Two apertures were apart; the gun ended from a nickel crystal cut parallel to its planes. An adjustable electric potential difference set the speed. The beam struck normally inside an evacuated, field-free enclosure with target and outer electrodes at one potential. A double-box collector, from the target with a entrance, selected directions. A retarding electric potential difference rejected slower Electrons; the inner collector fed a sensitive galvanometer. Moving the collector scanned colatitude; rotating the crystal scanned azimuth.[ref]
Diffraction of Electrons by a Crystal of Nickel by C. Davisson and L. H. Germer. The apparatus, printed pp. 707–710, figures 2–4: source, apertures, potentials, collector and target preparation
The readout was collected electric current, not a photograph of Electron paths. Voltage scans held the gun-plate current constant because incident-beam current could not be held constant; the overall current trend therefore needed caution. A strong feature developed at near colatitude. Surface heating distinguished crystal beams from adsorbed-gas beams; finite apertures and background shifted or broadened apparent peaks.[ref]
Diffraction of Electrons by a Crystal of Nickel by C. Davisson and L. H. Germer. Printed p. 705, abstract; pp. 715–719, figures 9–12: voltage-scan control, 54 V feature, background subtraction and instrumental widths
At the bright beam's colatitude, an azimuth scan revealed three companion directions, matching crystal symmetry. The test compared wavelengths inferred from diffraction angles and known crystal spacings with wavelengths inferred from accelerating voltage and momentum; the 1937 lecture displayed this comparison against . Agreement across beam directions supplied more evidence than one angular peak.[ref]
The discovery of electron waves by Clinton J. Davisson. Printed pp. 391–393, figures 2–4: angular and azimuth scans and independent wavelength comparison
The inference is about coherent quantum phases in scattering probabilities. It does not establish a wavy particle trajectory, and a collector-current experiment does not resolve individual detection events. Predicting the full intensity additionally requires the material's scattering amplitude, its surface condition, and instrumental angular acceptance; the de Broglie wavelength alone predicts none of those strengths. The following finite-row electron diffraction model isolates phase addition without attempting to reproduce the nickel measurements.