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*Schrödinger 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 inquantum chemistry. Also in the*nuclear shell model*angular momentum coupling is ubiquitous.[1][2]
In*astronomy,*spin-orbit coupling*reflects the general law ofconservation 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."
http://en.m.wikipedia.org/wiki/Angular_momentum_coupling
Hey! What does ubiquitous mean? Is it different than omnipresent?
Frequency gets a mention too... nuclear shell model... spectroscopy, I believe we covered that...