Adiabatic following condition for pulse propagation in three-level medium

The adiabatic following condition for the propagation of pulses in a three-level medium has been obtained. It is shown that the adiabatic criterion depends not only on the total Rabi frequency and pulse duration, but on the relationship between oscillator strengths of electric dipole transitions in an atom too. In particular, for (Lambda) - system if the oscillator strength for the pump transition is less or equal to that for the Stokes transition, the adiabatic following condition is preserved at arbitrary penetration depths. Otherwise it breaks down rather quickly with the distance of propagation.