Soft X‑ray\nInduced Radiation Damage in Dip-and-Pull\nPhoton Absorption and Photoelectron Emission Experiments

X-ray irradiation can induce chemical reactions on surfaces.\nIn\nX-ray spectroscopic experiments, such reactions may result in spectrum\ndistortion and are termed radiation damage. In this study, we investigate\nthe X-ray-induced chemical reaction at the partially oxidized copper\nsurface in the settings of the dip-and-pull experiment, a method that\ngenerates liquid–solid interfaces for in situ X-ray photoelectron\nspectroscopy (XPS) studies. In dense water vapor resembling the predipping\ncondition, a series of time-elapsed X-ray absorption spectra acquired\nin total electron yield mode (TEY-XAS) shows that X-ray exposure causes\ncopper reduction, which follows first-order kinetics and occurs only\nat the surface shallower than the probing depth of TEY-XAS. At the\nsolid–water interface created by the dip-and-pull method, the\nchemical reduction of surface copper is also identified by XPS. We\nconclude that the reduction is driven by the product of water radiolysis,\nwhere the reducing solvated electron prevails against the oxidizing\nOH radical and results in an overall reduction of surface copper ions.