Spectroscopy of a single adsorbed atom

We have used a low-temperature ultrahigh-vacuum scanning tunneling microscope to perform atomically localized spectroscopic measurements on single Fe atoms adsorbed onto the Pt(111) surface. Using a simple tunneling model, we are able to quantitatively deconvolute the tip and adatom local densities of states (LDOS) from the dI/dV spectra. We find that a resonance occurs in the adatom LDOS that is centered 0.5 eV above the Fermi energy. This feature has a width of approximately 0.6 eV, and occurs only when the tip is within angstroms (laterally) of the center of an Fe adatom.