J. Riga

A photoelectron spectroscopic study of the electrochemical processes in polyaniline

The electronic structure of the base forms of electrochemically prepared polyaniline is studied by means of x‐ray photoelectron spectroscopy (XPS). Model compounds for the amine, imine and crosslinked nitrogen sites provide the references for the analysis of the core level spectra in the polymer. In particular, the analysis of the nitrogen 1s spectra represents a useful method for accurate determination of the amine to imine ratio. The evolution in the concentration of the different nitrogen species as a function of the electrochemical potential is shown to be in good agreement with the results of cyclic voltammetry measurements. Varying the pH leads to large modifications in the stability domain of the different oxidation states.

Polymer primary structures studied by ESCA and EHCO methods

The electronic structure (core and valence levels) of various simple polymers has been investigated by ESCA (Electron Spectroscopy for Chemical Analysis), with the aid of original EHCO (Extended H?ckel Crystalline Orbitals) calculations giving corresponding density of states and band structure schemes. Simple monosubstituted homopolymers derived from polyethylene ([CH2-CHX]n) have been chosen in order to study the influence of X substituents (X = -F, -Cl, -OH, -CH3, -CH2CH3, -C6H5, -C6H11 corresponding respectively to poly(vinyl fluoride), poly(vinyl chloride), poly(vinyl alcohol), poly(propylene), poly(1-butene), poly(styrene), and poly(vinyl cyclohexane)) through the chemical shifts measured for the core levels, and the alteration of the valence band structures. Assignment of the valence molecular orbitals is made with the aid of the theoretical calculations and with comparison of spectra recorded for molecules similar to the monomeric units. Emphasis is put on the very significant information provided by the valence band spectra for polymers containing only carbon and hydrogen atoms. Valence band data are used to calculate physical parameters (first ionization potential, energy gap, work function) of importance to deduce electrical properties for the polymers.

Electronic structure of linear fluoropolymers : theory and ESCA measurements revisited

Abstract The valence electronic structure of polyethylene and of linear fluoropolymers is reinvestigated by a LCAO-CO method. Photoionization cross-section modu

Electronic Structure of Rutile Oxides TiO2, RuO2 and IrO2 Studied by X-ray Photoelectron Spectroscopy

Valence band X-ray photoelectron spectra of the rutile oxides TiO2, RuO2, and IrO2 show a distinct evolution as a function of the increasing number of metal d-electrons. The observations are found to be in excellent agreement with recent theoretical models. Intensity analysis and photo-ionization cross sections are used to confirm the nature of the band responsible for conducting properties. The result is in accordance with a crystal field model proposed earlier. The deduced number of free electrons in the valence band is used to correlate the asymmetry recorded for the core level lines.

Shake-up satellites in the x-ray photoelectron spectra of uranium oxides and fluorides. A band structure scheme for uranium dioxide, UO2

Abstract The analysis of the shake-up satellites recorded in core-level photoelectron spectra of uranium oxides and fluorides is used to understand the electronic structure of the valence and conduction bands of the solids. This study is shown to support the view that U 3 O 8 and U 2 O 5 are made of U(IV) and U(VI) species comparable to those in UO 2 and UO 3 . A model proposed for charge transfer in transition metal compounds is used, and an interpretation of these satellites is presented, that results in the location of the 6d conduction band of UO 2 at about 4 eV above the Fermi level of the sample.

A Comparative E.S.C.A. Study of the Electronic Structure of Solid Acenes: benzene, naphthalene, anthracene, and tetracene

By comparison of the E.S.C.A. valence band spectra recorded in the solid phase for polyacenes (benzene, naphthalene, anthracene, and tetracene) with gas phase results, important energy parameters (energy gap, work function) of these compounds have been obtained. The trends observed in the evolution of the main C1s shake-up positions and intensities serve to assign the π satellites to transitions of the type nb1 → b1*.

Electronic structure of polyaniline and substituted derivatives

Abstract Electronic structure of polyaniline prepared under two different potentials has been studied by x-ray photoelectron spectroscopy. In both cases, two different compounds are obtained. Polymer degradation is shown to occur only at 1.2 V. Protonation level and polymer structure in the substituted polyanilines are discussed.

X-ray photoelectron spectra of uranium and uranium oxides. Correlation with the half-life of 235Um.

Abstract Uranium metal and the uranium oxides UO 2 , U 3 O 8 , UO 3 are studied by photoelectron spectroscopy. Chemical shifts of the 4f electronic cor

An ESCA study of the electronic structure of solid benzene.: Valence levels, core level and shake-up satellites

The solid-state X-ray photoelectron spectrum of benzene is compared to gas-phase results and interpreted with the aid of theoretical models of its electronic structure. From a detailed analysis of the C1s core level, its shake-up satellites, and the valence band, molecular and solid-state parameters are determinated for the compound.

Penetration depth of tin in float glass

Abstract Experimental results on float glass by recent analytical techniques — ESCA, photon emission induced by ion bombardment and ellipsometry — support the conclusion that tin from a metal bath penetrates with relatively high concentration only in the first few nanometers from the surface.