Multi-photon absorption of molecules

Recent applications of response theory formulations of Olsen and Jorgensen on multi-photon absorption of molecules have been briefly reviewed. The connection between the calculated microscopic and experimentally measured macroscopic properties is derived. The performance of various computational approaches ranging from Hartree-Fock and Coupled Cluster to Density Functional theory for these spectral properties is analyzed. Using analytic response theory results as reference, the validity of the commonly applied few-states models for two- and three-photon absorption of molecules have been examined. A design strategy for three-dimensional charge-transfer multi-photon absorption systems is presented.