File Name : wasserfall_si.pdf

Caption : electron binding energy spectra of ag$_{91}^-$ taken at photon energies as indicated. the data \nitext{recorded} at high photon energies reveal that the major fraction of the mapped density of states is found at higher binding energies, i.e. above  $e_{bin}=3.3$~ev. due to the spectrometer transmission function, this region is strongly suppressed when probed at lower photon energies, see for example the spectrum recorded at $e_{ph}=3.56$\,ev. for method i, this results in a correction factor of up to $c=8$. \nitext{regarding the low binding energy feature, one can see} that the center of gravity of the peak changes with photon energy. we checked that this has no impact on the correction procedure as every integration (eq.\,4) includes the entire region at least up to the dashed line. for the presentation, the spectra are normalized to the integrated yield of the low binding energy peak, i.e. up to $e_{bin}=3.28$~ev.