THE DEVELOPMENT OF CORE ELECTRON SPECTROSCOPIES OF ADSORBATES

A short historical survey is given of the development of applications of core electron spectroscopies (X-ray induced core photoelectron spec troscopy, XPS; and Auger electron spectroscopy, AES) in surface physic s, in particular in the investigation and characterization of well-def ined adsorbate layers on single crystal surfaces. A personal perspecti ve is used to show, with this subject and partly the author's group as example, the sometimes winding ways on which ideas and insights jump between communities, and the importance of personal relations in this process. Topics mentioned include qualitative and quantitative analysi s of adsorbate species, interpretation of binding energy shifts induce d by adsorption and connected topics such as reference levels, local p otential, relaxation/screening and charge transfer, as well as final s tate splitting, satellites, peak shape changes and angular effects in both photo- and Auger electron spectra. The newly accessible possibili ties from very high resolution in photon source and electron analysis, coupled with selective excitation with synchrotron radiation, are bri efly discussed, and emphasis is laid on the access by these means to e lectronic dynamics and to their coupling to the dynamics of atomic mot ion, as visible in fragmentation of adsorbed molecules by these electr onic excitations.