We propose to study x-ray transient absorption in model gaseous systems as a function of intensity using broad
bandwidth, ultrashort pulses emanating from the EuXFEL. In particular, we focus on a quantitative understanding of
deviations from a linear absorption model that are expected when the incident intensity is increased. Processes
associated with high-intensity x-ray propagation through resonant media include stimulated resonant Raman scattering,
amplified spontaneous emission and pulse compression. Our theoretical simulation based upon a combined
TDSE/Maxwell equation approach provides a 3D description of the transverse as well as longitudinal variation along the
x-ray propagation axis. We will address the following questions: In the weak-field regime, can SASE pulses be used to
obtain single-shot absorption spectra, and, to perform x-ray pump-probe studies within a single pulse? In the strong-field
regime, can propagation through dense resonant media be accurately modeled?