Coherent dynamics ofN-level atoms and molecules. III. An analytically soluble periodic case

By employing an analogy with a spin-J system in a constant magnetic field the authors obtain a simple soluble model for stepwise laser excitation of an N-level system ($N=2J+1$), including analytic treatment of Doppler detuning and of ionization loss. The solutions are periodic and hence permit complete population inversion. A simple graphical realization of the population dynamics, a generalization of the Feynman, Vernon, and Hellwarth vector model of the two-level Bloch equation, is then described.