Lineshapes in core-level photoemission from metals .3. Site-dependent screening in the charge density wave materials 1T- and 4H(b)-TaS2

High-resolution x-ray photoemission (XPS) studies of the lineshapes of the Ta 4f core levels in 1T- and 4H(b)-TaS2 are reported. These materials show charge density wave (CDW) behaviour at room temperature, and the local electron densities at different atomic sites are shown to produce different local screening of the core-level photohole, so the components of the doublet or tripler 4f emission line resulting from the CDW-induced shifts in the local potential at different atomic sites have different core line asymmetries. The complex lineshapes are analysed using the iterative fixing procedure, SHAPER, allowing connections to be made between the observed spectra and the site-dependent density of states.