Surface core level shifts in photo-electron spectra from the Ca, Sr and Ba titanates

Photoelectron binding energy (BE), shifts observed in core level spectra of Ca, Sr and Ba present at the outer most surface with respect to the bulk in the respective single crystal titanates can be correlated to the inverse of their respective electro-negativities. Such trends can be explained within the context of the charge potential model. This model, which does not account for final state effects, indicates that (a) the direction of the BE shift results from chemical environment variations (an inter-atomic effect sometimes referred to in Madulung constant terms), and (b) BE shift variations result from electron density variations on the atom the photo-electron emanated from (an intra-atomic effect, which can also be relayed in ionic radii and electro-negativity terms).