A new approach explains the nature of a coherent state as a macroscopic collection of in-phase precession states. The latter are the most general solution to the problem of describing a system under spin-orbit interaction. The precession states owe their name to a periodic exchange of part of their sublevel populations which is the quantum-mechanical equivalent of the classical precession. Due to an unbalanced exchange of population the precession states cannot be stationary fine-structure eigenstates. But if the initial sublevel populations are proportional to the Clebsch-Gordan coefficients, the exchange becomes balanced thus independent of time and unobservable, turning the general precession state into a stationary fine-structure eigenstate.
