Probing exciton dynamics using Raman resonances in femtosecond x-ray four-wave mixing

Time-resolved coherent x-ray Raman signals of molecules are computed by formulating the nonlinear response in terms of correlation functions of charge and current densities. Simulations performed on one-dimensional molecular chains demonstrate that Raman resonances provide a direct local probe for valence-excitation dynamics with high spatial and temporal resolutions.