Line shapes in surface-atom core-level photoemission from Ta(111), W(111), and W(100)

Photoemission data for the $4f$ levels of oriented, clean surfaces of W and Ta have been reanalyzed, using improved descriptions of the line shape and background. The results confirm the earlier values for the surface and subsurface core-level shifts and intensities, and yield new values for the lifetime widths and singularity indices which remove previously noted inconsistencies. The surface components were found to have different Gaussian broadening in the two spin-orbit lines. This indicates that the broadening can be due only in part to surface phonon excitation. The rest is tentatively attributed to unresolved surface crystal-field splitting.