Multi-frequency molecular excitation by FEL radiation with adiabatically changing frequency for laser chemistry applications

Molecular excitation by a laser field with a slowly changing frequency is considered. This regime can be realised on FELs with a periodic injection of the electron beam. The laser field required to excite the vibration levels of the molecules is substantially lower than in the case of excitation by a laser field with a constant frequency. The conditions which are necessary for the realisation of this regime are discussed in this paper.