  The Bethe-Salpeter equation (BSE) is a powerful theoretical approach that is
capable to accurately treat electron-hole interactions in materials in an
excited state. We developed an ab initio framework based on the BSE to describe
a pump-probe experiment, in which an x-ray pulse probes solid-state valence
excitons by means of x-ray absorption spectroscopy. Our theoretical framework
is of relevance for an accurate modeling of pump-probe experiments of
photo-excited materials that utilize novel capabilities offered by x-ray
science.
