Band effects in the 5p levels of Ho(0001)

Recent band structure calculations have indicated that the 5 p core levels of the lanthanide metals may influence the bonding significantly. The authors have investigated this possibility with angle-resolved UV photoemission from the 5 p levels of Ho(0001), using synchrotron radiation. Spectra taken at normal and off-normal emission show a changeover in the relative intensities of the 5p 1/2 and 5p 3/2 peaks, and the spectra taken at equal emission angles either side of the surface normal (for a constant photon incidence angle) are found to differ significantly. As these phenomena would not occur if the 5 p levels were 'true' core levels, i.e. showing negligible dispersion, the authors conclude that they must have a significant bandwidth.