Angular-momentum algebra and ladder spectrum
Quantum angular momentum obeys [J_i,J_j]=iħ ε_ijk J_k.
Key knowledge
Quantum angular momentum obeys [J_i,J_j]=iħ ε_ijk J_k. Simultaneous eigenstates of J² and J_z have eigenvalues ħ²j(j+1) and ħm, with m=−j,…,j; J_± raises or lowers m by one with coefficient ħ√[j(j+1)−m(m±1)].
Values and equations
J²|j,m⟩=ħ²j(j+1)|j,m⟩; J_z|j,m⟩=ħm|j,m⟩; J_±=J_x±iJ_y
- J_i,J_±
- Angular-momentum operators J s
- J²
- Squared total angular momentum J² s²
- ħ
- Reduced Planck constant J s
- j,m,ε_ijk
- Dimensionless labels and Levi-Civita symbol
- |j,m⟩
- Normalized simultaneous eigenstate
Conditions and scope
- Usual finite angular-momentum representations: j nonnegative integer or half-integer; orbital single-valued wavefunctions have integer l.
- Components do not have simultaneous sharp values; products require a suitable domain.
Sources · 2
References
Sources retain their recorded scope. A source link alone does not establish verification of every statement.
Richard Fitzpatrick / University of Texas at Austin2 sources
Evidence and review
Quantum Mechanics (2016): Eigenvalues of orbital angular momentum: Equations 4.25–4.56: spectrum and normalized ladders. Quantum Mechanics (2016): Commutation rules: Equations 6.1–6.6: general integer/half-integer angular momenta.
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Entry details
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