  We theoretically investigate the incident-photon energy omega_i dependence of
resonant inelastic x-ray scattering (RIXS) tuned for the Cu L edge in cuprate
superconductors by using the exact diagonalization technique for a single-band
Hubbard model. Depending on the value of core-hole Coulomb interaction in the
intermediate state, RIXS for non-spin-flip channel shows either a
omega_i-dependent fluorescencelike or omega_i-independent Raman-like behavior
for hole doping. An analysis of x-ray absorption suggests that the core-hole
Coulomb interaction is larger than on-site Coulomb interaction in the Hubbard
model, resulting in a fluorescencelike behavior in RIXS consistent with recent
RIXS experiments. A shift on the high-energy side of the center of spectral
distribution is also predicted for electron-doped systems though spectral
weight is small. Main structures in spin-flip channel exhibit a Raman-like
behavior as expected, accompanied with a fluorescencelike behavior with small
intensity.
