On the propagation of electromagnetic pulses under the conditions of quasi-resonance

A theory of quasi-resonance for the model of atoms with an arbitrary number of levels is developed by the method of unitary transformation without rec ourse to Bloch's equations. Corrections to the results known from the theor y of adiabatic following, which refine these results and take into account dispersion of the nonlinear response of the resonant system, are obtained. The condition for quasi-resonance with a single atomic transition is shown to impose stringent limitations on the form of the nonlinear evolution equa tion for the electric field envelope of the pulse with dispersion of the no nlinear response taken into account, which prohibit the reduction of the eq uation indicated to familiar, fully integrable systems. (C) 2000 MAIK "Nauk a/Interperiodica".