Theory of ultrafast non-resonant multi-photon transitions: basics and application to CpMn(CO)3

Femtosecond laser pulse control experiments including non-resonant multiphoton transitions (NMT) are described theoretically. In order to apply optimal control theory for the computation of the pulse shape, an effective Schrِdinger equation is derived. It contains effective coupling terms which account for any type of NMT processes. The general approach is applied to the two-photon non-resonant transition in the organometallic compound CpMn(CO)3 which has been recently analyzed experimentally as well as theoretically in [C. Daniel et al. Science 299 (2003) 536]. The computations demonstrate that the whole methodology is ready to study a broad class of NMT experiments in the gaseous phase as well as in the condensed phase (upon generalization to a density matrix description).