Population inversion in a multilevel system: a model study

For most isolated molecules, the generation of a π-pulse which will create complete inversion of the population of two electronic states is impossible because the rotational contribution to the transition dipole moment is an explicit function of the projection of the total angular momentum along the electric field axis. It is, however, possible to obtain nearly complete inversion by use of phase- and amplitude-modulated pulses; we show examples of such inversion with scaled and swept hyperbolic secant pulses. We report the results of pulse shape calculations for model systems with one and eight transition dipole moments