Weak and strong spin–orbit Zeeman regimes
At leading electron g_s=2, a uniform magnetic field along z adds H_B=μ_BB(L_z+2S_z)/ħ, μ_B=eħ/(2m_e).
Key knowledge
At leading electron g_s=2, a uniform magnetic field along z adds H_B=μ_BB(L_z+2S_z)/ħ, μ_B=eħ/(2m_e). For a weak field relative to the spin–orbit splitting, ΔE≈μ_BBg_jm_j with g_j=1+[j(j+1)+s(s+1)−l(l+1)]/[2j(j+1)] and s=½. When magnetic coupling dominates spin–orbit but remains small relative to other orbital scales, the Paschen–Back leading shift is μ_BB(m_l+2m_s).
Values and equations
H_B=μ_BB(L_z+2S_z)/ħ; ΔE_weak=μ_BBg_jm_j; ΔE_PB≈μ_BB(m_l+2m_s)
- H_B,ΔE
- Magnetic energy operator/shift J
- B
- Magnetic flux density magnitude T
- μ_B
- Bohr magneton eħ/(2m_e) J T⁻¹
- L_z,S_z,ħ
- Angular-momentum components and reduced Planck constant J s
- g_j,j,l,s,m_j,m_l,m_s
- Dimensionless factors and angular labels
Conditions and scope
- Central-field single-electron states, uniform static field and perturbative magnetic coupling relative to principal orbital spacings; weak/strong comparison is with the relevant actual spin–orbit gap, not a universal field in tesla.
- The quadratic diamagnetic term, nuclear/hyperfine coupling, anomalous spin moment and unresolved close orbital degeneracies require additional terms. The strong-field formula neglects the residual spin–orbit correction.
Sources · 2
References
Sources retain their recorded scope. A source link alone does not establish verification of every statement.
Evidence and review
Quantum Mechanics (2016): Zeeman effect: Equations 7.124–7.134: SI operator, weak Landé factors and strong-field uncoupled shift; equations 7.136–7.139 retain residual spin–orbit correction. Excludes the example-specific approximately 25 T threshold as a universal value. Quantum Physics III: chapter 2, fine structure: §2.5 equations 2.5.20–2.5.22, printed page 48: general orbital/spin Landé factor; Gaussian Bohr magneton converted using the explicit SI operator from the other source.
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