  Self-assembled Au atomic wires on stepped Si surfaces are metallic, as
evidenced by a one-dimensionally dispersing plasmonic excitation. Here we
investigate the effects of oxidization on metallicity along such Au atomic
wires on a regularly stepped Si(553) surface, by employing infrared absorption
and high resolution electron energy loss spectroscopies. Our results indicate
that only the Si environment undergoes oxidation, which has a remarkably small
effect on the plasmon dispersion. Only close to $k_{\parallel}\rightarrow 0$
the plasmon dispersion ends at increasingly higher energies as a function of
oxygen exposure, which is attributed to standing wave formation on small
sections of Au wires generated by the introduction of O atoms as scattering
centers, not to electronic gap opening. This interpretation is in full
agreement with the findings by infrared spectroscopy and with low energy
electron diffraction.
