Stern–Gerlach experiment

A 1922 experiment sent silver atoms through an inhomogeneous magnetic field and found two distinct deflections, demonstrating quantized angular-momentum projections.

Magnetic dipole: A magnetic dipole is a system with a magnetic moment that produces a dipole-shaped magnetic field. Each silver atom behaves as a magnetic dipole whose moment couples to the field gradient.
Otto Stern: Otto Stern was a German physicist who proposed and co-led the experiment. Stern conceived the test to investigate quantization in atomic magnetic moments.
Silver: Silver is a chemical element with atomic number 47 and one electron outside a filled inner shell. Its ground-state atoms have one unpaired electron and a net magnetic moment.
Stern–Gerlach apparatus: The Stern–Gerlach apparatus is a vacuum device with an oven, collimating slits, a shaped magnet, and a detector. Its asymmetric magnet created the gradient that converted magnetic projections into spatial separation.
Spin-1/2: Spin-1/2 is a quantum angular-momentum class whose measured component has two possible values. The silver beam’s two outcomes became a textbook illustration of spin-1/2 measurement.
Magnetic-field gradient: A magnetic-field gradient is spatial variation in a magnetic field’s strength or direction. The field gradient, rather than a uniform field, exerts a net force that separates the beam.
Walther Gerlach: Walther Gerlach was a German experimental physicist who co-led the experiment. Gerlach designed and operated the apparatus that produced the separated beam.
Silver atom: A silver atom is an atom of element 47, with 47 protons and typically one outer 5s electron. The experiment used neutral silver atoms because their magnetic moments were comparatively simple.
Silver beam splitting: Silver beam splitting is the separation of an atomic beam into distinct components by magnetic deflection. The two deposited traces were the experiment’s central observation.
Quantum state preparation: Quantum state preparation is the controlled creation of a system in a specified quantum state. A selected output beam can prepare atoms with a known angular-momentum projection.

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