In

quantum mechanics, the procedure of constructing eigenstates

? of total

angular momentum out of eigenstates

? of separate angular momenta is called

**angular momentum coupling**. For instance, the orbit

? and

spin of a single particle can interact through spin-orbit interaction

?, in which case the complete physical picture must include

spin-orbit coupling. Or two charged particles, each with a well-defined

angular momentum, may interact by Coulomb forces

?, in which case coupling of the two one-particle angular momenta to a total

angular momentum is a useful step in the solution of the two-particle

SchrÃ¶dinger equation. In both cases the separate angular momenta are no longer constants of

motion, but the sum of the two angular momenta usually still is.

**Angular momentum coupling** in atoms is of importance in atomic spectroscopy

?.

**Angular momentum coupling** of

electron spins is of importance in quantum chemistry

?. Also in the nuclear shell model

**angular momentum coupling** is ubiquitous.

In

astronomy,

spin-orbit coupling reflects the general law of conservation of angular momentum

?, which holds for celestial systems as well. In simple cases, the direction of the

angular momentum vector is neglected, and the

spin-orbit coupling is the

ratio between the

frequency with which a planet or other celestial body spins about its own axis to that with which it orbits another body. This is more commonly known as orbital resonance

?. Often, the underlying physical effects are tidal forces. (wikipedia)

See Also

**angular momentum**
**Connecting Link**
**coupling**
**momentum**
**Quantum coupling**
**Quantum Entanglement**
**Rotational-vibrational coupling**
**Rovibrational coupling**
**rovibronic coupling**
**Sympathetic Oscillation**
**Sympathetic Vibration**
**Sympathy**
**Vibronic coupling**