We report a new method to probe the solid-liquid interface through the use of a thin liquid layer on a solid surface. An ambient pressure XPS (AP-XPS) endstation that is capable of detecting high kinetic energy photoelectrons (7 keV) at a pressure up to 110 Torr has been constructed and commissioned. Additionally, we have deployed a “dip & pull” method to create a stable nanometers-thick aqueous electrolyte on platinum working electrode surface. Combining the newly constructed AP-XPS system, “dip & pull” approach, with a “tender” X-ray synchrotron source (2 keV–7 keV), we are able to access the interface between liquid and solid dense phases with photoelectrons and directly probe important phenomena occurring at the narrow solid-liquid interface region in an electrochemical system. Using this approach, we have performed electrochemical oxidation of the Pt electrode at an oxygen evolution reaction (OER) potential. Under this potential, we observe the formation of both Pt2+ and Pt4+ interfacial species on the Pt working electrode in situ. We believe this thin-film approach and the use of “tender” AP-XPS highlighted in this study is an innovative new approach to probe this key solid-liquid interface region of electrochemistry.

The examination of the surface deposit of various lichens with X-ray diffraction methods, correlated with scanning electron microscopical (SEM) studies, have shown that calcium oxalate is present as two different hydrates; weddellite (CaC2O4-(2 + x)H2O), in three slightly different morphologies, and whewellite (CaC2O4H2O). The reason for the formation of calcium oxalate is not known and the presence of the various crystal forms is yet to be explained. However, the various hydrates may have some role in the water balance as they are different in dry and humid sites.

No abstract

No abstract

Solutions of fatty acid potassium salts in formamide have been investigated using electron spectroscopy in the angular resolved mode. The variable surface sensitivity thus achieved allows details of the electric double layers formed at the solution surfaces to be investigated. The cation distribution is found to vary as a function of solution concentration. The simple diffuse layer theory based on the Poisson–Boltzmann equations is found inadequate in describing the observed features. The data suggest that structural changes occur at the higher concentrations forming closer bound cation states at the surface. These findings qualitatively confirm recent theoretical model predictions by other workers.

No abstract

No abstract

The threshold behavior of the single-photon double-ionization cross section of atomic oxygen has been studied using vacuum uv radiation from a synchrotron storage ring. The double-ionization cross section appears to follow a power law E (where E is the kinetic energy of the two electrons) from its threshold to about 2.0 eV above with an exponent o. = 1.08~0.03 which is consistent with Wannier's theoretical value of 1.056.The cross section also shows the influence of the doubly excited 2s2p nln'l' (n, n') 3) neutral states, among which the first three converge to the 2s2p ( S')4p( P') ionic state of oxygen.PACS number(s): 32.80.Dz, 32.80.Fb