Chemical-state-specific surface structure determination

As surface science advances to studies of increasingly complex surface phases, such as the coadsorption states present during surface chemical reactions, there is an increasing need for local quantitative structural probes which can provide information which is both element and chemical-state specific. Current progress in two such methods is reviewed briefly. Both methods exploit the well-known chemical shifts of core level photoelectron binding energies, while the structural information derives from photoelectron diffraction and X-ray standing waves. Both methods require a combination of high photon flux and high spectral resolution in the soft X-ray energy range, and so are beginning to benefit strongly from undulator sources on third-generation synchrotron radiation sources.