Electron spin

Electron spin is an intrinsic quantum angular momentum carried by every electron. It gives electrons a magnetic moment and allows only two spin projections along any chosen axis.

Spin quantum number: A quantum number specifying a particle’s intrinsic angular momentum; an electron has spin quantum number one-half. It fixes the magnitude of an electron’s intrinsic angular momentum.
Angular momentum: A physical quantity associated with rotational motion, conserved in systems with rotational symmetry. Spin is an intrinsic form of angular momentum, not orbital motion.
Electron paramagnetic resonance: A spectroscopy technique that detects unpaired electron spins through their microwave absorption in a magnetic field. It measures spin transitions to identify radicals and paramagnetic centers.
Orbital angular momentum: Angular momentum arising from a particle’s spatial motion around a reference point. Unlike orbital angular momentum, electron spin exists without spatial circulation.
Spin projection: The component of a particle’s angular momentum along a chosen measurement axis. An electron’s projection along any chosen axis has two possible values.
Quantum number: A value labeling a quantized property or state in a quantum system. Spin is specified by quantum numbers rather than a classical orientation.
Spintronics: A field of electronics that uses electron spin as well as electric charge to store or process information. It treats spin as a controllable information-bearing degree of freedom.
Classical spinning top: A rigid body rotating about an axis with ordinary mechanical angular momentum. Electron spin follows quantum rules and is not literal rotation of a tiny sphere.
Stern–Gerlach experiment: An experiment that separates particles by magnetic moment using a nonuniform magnetic field. Its two-beam result revealed discrete spin projections for silver atoms.
Fermion: A particle with half-integer spin that obeys Fermi–Dirac statistics. Electrons belong to the half-integer-spin particle family.

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