  We present a novel derivation of resonant inelastic x-ray scattering (RIXS)
which yields an expression for the RIXS cross section in terms of emission
pathways between intermediate and final many-body states. Thereby electron-hole
interactions are accounted for, as obtained from full diagonalization of the
Bethe-Salpeter equation within an all-electron first-principles framework. We
demonstrate our approach with the emission spectra of the fluorine K edge in
LiF, and provide an in-depth analysis of the pathways that determine the
spectral shape. Excitoninc effects are shown to play a crucial role in both the
valence and core regime.
