  The ladder compound Sr$_{14}$Cu$_{24}$O$_{41}$ is of interest both as a
quasi-one-dimensional analog of the superconducting cuprates and as a
superconductor in its own right when Sr is substituted by Ca. In order to model
resonant inelastic x-ray scattering (RIXS) spectra for this compound, we
investigate the simpler SrCu$_{2}$O$_{3}$ system in which the crystal structure
contains very similar ladder planes. We approximate the LDA dispersion of
SrCu$_{2}$O$_{3}$ by a Cu only two-band tight-binding model. Strong correlation
effects are incorporated by assuming an anti-ferromagnetic ground state. The
available angle-resolved photoemission (ARPES) and RIXS data on the ladder
compound are found to be in reasonable accord with our theoretical predictions.
