The time- and frequency-resolved nonlinear light scattering (NLS) signals from a time-evolving charge distribution of valence electrons prepared by impulsive x-ray pulses are calculated using a superoperator Green's function formalism. The signal consists of a coherent $\sim$$N^2$-scaling difference-frequency-generation and an incoherent fluorescence $\sim$$N$-scaling component, where $N$ is the number of active molecules. The former is given by the classical Larmor formula based on the time-dependent charge density. The latter carries additional information about the electronic structure and may be recast in terms of transition amplitudes representing quantum matter pathways.

• Received 31 December 2012

DOI:https://doi.org/10.1103/PhysRevA.87.053826