Quasienergy derivative method for the optical susceptibilities of molecules in the floquet theory
Résumé
The Hellmann-Feynman theorem in time-extended Hilbert space is applied to the Floquet states of a molecule in the multifrequency field of a light wave. It is shown that the formula expressing the dynamic susceptibilities of a molecule in terms of the quasienergy derivatives with respect to the field amplitudes contains a numerical factor ensuring correct asymptotics of the susceptibilities in the static limit. This factor determines the relationship between the static Stark effect and the shift of the quasienergy level at ω → 0 in each order of perturbation theory. © 2005 Pleiades Publishing, Inc.