Multiphoton absorption by molecules

Rabi frequencies for multiphoton absorption by atoms or molecules that can be characterized as two- or three-level systems are obtained in the cases of single and double laser perturbations. If the ambiguity in the origin of absolute energy is conveniently gauged off in the three-level model, there appears an additional non-linear frequency which originates from the separate evolution of a relative frequency component induced in the whole system by the simultaneous action of the two perturbations. (C) 1998 Elsevier Science B.V. All rights reserved.