NONRESONANT INTERACTION OF ULTRASHORT ELE CTROMAGNETIC PULSES WITH MULTILEVEL QUANTUM-SYSTEMS

A theoretical investigation is made of a multilevel quantum system exc ited by an electromagnetic pulse whose duration is much less than the reciprocal of the interlevel transition frequency. It is shown that th e interaction is characterized by a new type of selectivity that is no t caused by utilization of resonance properties of a substance, but is associated with the selection rules for the transitions between the l evels and with the equality to zero of the ''area'' defined by the int egral of electromagnetic field strength. This selectivity mechanism is found to be efficient in forming nonequilibrium states in multilevel quantum systems and, in particular, a nonresonant excitation and disso ciation of molecules by femtosecond electromagnetic pulses is shown to be feasible.