  We report a Cu K- and L$_3$-edge resonant inelastic x-ray scattering study of
charge and spin excitations of bulk Nd$_{2-x}$Ce$_x$CuO$_4$, with focus on
post-growth annealing effects. For the parent compound Nd$_2$CuO$_4$ ($x = 0$),
a clear charge-transfer gap is observed in the as-grown state, whereas the
charge excitation spectra indicate that electrons are doped in the annealed
state. This is consistent with the observation that annealed thin-film and
polycrystalline samples of RE$_2$CuO$_4$ (RE = rare earth) can become metallic
and superconducting at sufficiently high electron concentrations without Ce
doping. For $x = 0.16$, a Ce concentration for which it is known that oxygen
reduction destroys long-range antiferromagnetic order and induces
superconductivity, we find that the high-energy spin excitations of
non-superconducting as-grown and superconducting annealed crystals are nearly
identical. This finding is in stark contrast to the significant changes in the
low-energy spin excitations previously observed via neutron scattering.
