Angle-resolved bremsstrahlung isochromat spectroscopy of Cu(100) and Cu(110)

Angle-resolved isochromat spectra from Cu(100) and Cu(110) have been measured. The results in terms of energy versus momentum dispersions are discussed and compared to theoretical data. This includes predictions on the basis of a one-step theory and predictions within the bulk direct-transition model. The experimentally obtained $E\left(\overrightarrow{\mathrm{k}}\right)$ points on the high-symmetry axes $\Gamma -\Delta -X$ and $\Gamma -K-X$ are also compared to results from angle-resolved photoemission spectroscopy. The present bremsstrahlung data fit in very well into the photoemission data. In particular, deviations from theory show the same sign and magnitude in both data sets. This encourages the conclusion that corrections to the one-electron energies in photoemission and bremsstrahlung spectroscopy on copper stay well below an upper limit of 0.3 eV.