  We investigate the electron-energy loss spectrum of one-dimensional undoped
CuO$_{3}$ chains within an extended multi-band Hubbard model and an extended
one-band Hubbard model, using the standard Lanczos algorithm. Short-range
intersite Coulomb interactions are explicitly included in these models, and
long-range interactions are treated in random-phase approximation. The results
for the multi-band model with standard parameter values agree very well with
experimental spectra of Sr$_{2}$CuO$_{3}$. In particular, the width of the main
structure is correctly reproduced for all values of momentum transfer. It is
shown for both models that intersite Coulomb interactions mainly lead to an
energy shift of the spectra. We find no evidence for enhanced intersite
interactions in Sr$_{2}$CuO$_{3}$.
