elektronspins

Electron spins, or elektronspins in Swedish, refer to the intrinsic angular momentum of electrons, a fundamental quantum property independent of their motion through space. For a free electron, the spin quantum number is s = 1/2, giving two possible projections along any chosen axis: m_s = +1/2 and m_s = -1/2. The electron carries a magnetic moment μ ≈ -g μ_B S/ħ, where μ_B is the Bohr magneton and g ≈ 2.0023 is the g-factor. Because of this magnetic moment, spins interact with magnetic fields and can align or anti-align with them.

In a magnetic field, spin states split in energy (Zeeman effect). The energy difference between the two spin states is ΔE = g μ_B B, leading to transitions that can be driven by electromagnetic radiation at characteristic frequencies. In atoms, electron spin couples with orbital angular momentum to form total angular momentum J, influencing spectra and chemical behavior. The Pauli exclusion principle and spin statistics arise from the spin-1/2 nature of electrons, underpinning the structure of atoms and the arrangement of electrons in matter.

In solids, electron spins contribute to magnetism, with collective alignment producing ferromagnetism, antiferromagnetism, and related phenomena. Spin-dependent transport enables spintronics, where spin currents and spin polarization are used alongside charge currents. Spin–orbit coupling links spin to momentum, affecting electrical and optical properties. Measurement techniques include the Stern-Gerlach experiment, electron spin resonance (ESR or EPR), and various magnetic resonance methods. Electron spins also serve as qubits in some quantum computing architectures, where their coherence and controllable manipulation are central concerns.