  We study density response N(k,omega) and one-particle spectra A(k,omega) for
a Wigner lattice model at quarter filling using exact diagonalization. We
investigate these observables for models with short and long-range
electron-electron interaction and show that truncation of the electron
repulsion can lead to very different results. The spectra show clear signatures
of charge fractionalization into pairs of domain walls, whose interaction can
be attractive or repulsive and is controlled by the formal fractional charges.
In striking contrast to a bound exciton in N(k,omega), we find an antibound
quasi-particle in A(k,omega), which undergoes spin-charge separation. We
present a case of extreme particle-hole asymmetry, where photoemission shows
spin-charge separation, while inverse photoemission exhibits an uncorrelated
one-particle band.
