Leading relativistic atomic operators
For an electron in a central electrostatic potential energy V(r), the leading low-velocity corrections to p²/(2m_e)+V are H_rel=−p⁴/(8m_e³c²), H_SO=V′(r)L·S/(2m_e²c²r) and H_D=ħ²∇²V/(8m_e²c²).
Key knowledge
For an electron in a central electrostatic potential energy V(r), the leading low-velocity corrections to p²/(2m_e)+V are H_rel=−p⁴/(8m_e³c²), H_SO=V′(r)L·S/(2m_e²c²r) and H_D=ħ²∇²V/(8m_e²c²). The spin–orbit coefficient includes Thomas's factor one-half; L·S=(J²−L²−S²)/2 for J=L+S.
Values and equations
H_rel=−p⁴/(8m_e³c²); H_SO=V′(r)L·S/(2m_e²c²r); H_D=ħ²∇²V/(8m_e²c²)
- H_rel,H_SO,H_D,V
- Energy operators and central potential energy J
- p
- Canonical momentum in this scalar-potential model kg m s⁻¹
- m_e
- Electron mass kg
- c
- Vacuum light speed m s⁻¹
- r
- Radial position m
- L,S,J
- Orbital, spin and total angular momentum J s
- ħ
- Reduced Planck constant J s
Conditions and scope
- Static central potential, spin-one-half electron, a controlled low-velocity expansion and consistent operator domains; external vector potential omitted. The Darwin operator can be distributional for a Coulomb point nucleus.
- Treat these as perturbations at the stated order, not as a globally bounded exact Hamiltonian. Radiative, recoil, hyperfine, finite-nuclear-size and anomalous-moment effects are excluded.
Sources · 1
References
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Evidence and review
Quantum Physics III: chapter 2, fine structure: §2.3, printed pages 33–35, equation 2.3.14: kinetic, spin–orbit and Darwin operators; §2.4.3 equation 2.4.52: coupled angular identity. Source uses Gaussian electromagnetic quantities, but its potential-energy form and mechanical operators are converted here without copying a Gaussian e/c coupling.
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