Resonant X-ray Raman scattering

A total of 43 polymers containing only C, H, and O have been studied using an X-ray photoelectron spectroscopy instrument capable of the highest energy resolution avallable to date. The primary alm was to reinvestigate the C1s binding energy shifts for oxygen functionalltles and to systematically investigate secondary (β) shifts for the first time. In addition, this large data set has revealed the effects of vibrational fine structure on C1s component line width/shape and the effects of shake-up/shake-off (in photoemission from C=O groups) on nonstoichoimetry of C1s component intensities

Primary and secondary oxygen-induced C1s binding energy shifts in X-ray photoelectron spectroscopy of polymers

Two different straightforward synthetic approaches are presented to fabricate long-range-ordered monolayers of a covalent organic framework (COF) on an inert, catalytically inactive graphite surface. Boronic acid condensation (dehydration) is employed as the polymerization reaction. In the first approach, the monomer is prepolymerized by a mere thermal treatment into nanocrystalline precursor COFs. The precursors are then deposited by drop-casting onto a graphite substrate and characterized by scanning tunneling microscopy (STM). While in the precursors monomers are already covalently interlinked into the final COF structure, the resulting domain size is still rather small. We show that a thermal treatment under reversible reaction conditions facilitates on-surface ripening associated with a striking increase of the domain size. Although this first approach allows studying different stages of the polymerization, the direct polymerization, that is, without the necessity of preceding reaction steps, is desi...

Synthesis of Well-Ordered COF Monolayers: Surface Growth of Nanocrystalline Precursors versus Direct On-Surface Polycondensation

Separate state vs. transition state Kohn-Sham calculations of X-ray photoelectron binding energies and chemical shifts

Multiply charged molecules

High-resolution C is and O is gas-phase X-ray photoelectron spectra of methyl isobutyrate, methyl methacrylate, methyl acrylate, acrylic acid, acetic acid and formic acid have been investigated as model compounds for solid poly(methyl methacrylate) (PMMA). Secondary chemical shifts, variations in peak shapes and intensities for the different core lines were observed. It is shown that asymmetries and differences in line widths of the component peaks should be considered for a correct analysis of the solid polymer spectra. The observed intensities of the different C 1s and O is peaks in the gas-phase spectra do not follow stoichiometric ratios owing to different shake-off/shake-up probabilities. The gas-phase core electron binding energies have been compared with ab initio ΔSCF calculations where the relaxation of the core-hole state was included. Using a group shift argument, the relationship between the gas-phase model molecule shifts and the solid PMMA shifts have been discussed and applied to the analysis of the PMMA spectra.

Experimental and theoretical XPS study of model molecules for poly(methyl methacrylate)

Experimental and theoretical study of the N1s and C1s shake-up satellites in pyridine and aniline

The S 2${\mathit{p}}_{3/2}$\char21{}S2 ${\mathit{p}}_{1/2}$ spin-orbit splitting is measured for the free ${\mathrm{H}}_{2}$S molecule using both high-resolution x-ray photoelectron spectroscopy (XPS) and high-resolution photon-excited Auger-electron spectroscopy. It is found that the spin-orbit splitting differs in the two experiments by as much as 50 meV. In contrast, the Ar 2${\mathit{p}}_{3/2}$\char21{}Ar 2${\mathit{p}}_{1/2}$ spin-orbit splitting is practically the same when comparing Auger and XPS data. The origin of the shift for ${\mathrm{H}}_{2}$S is discussed with respect to molecular field splitting and state interference effects.

Observation of an energy shift in the S2p3/2-S2p1/2 spin-orbit splitting between x-ray photoelectron and Auger-electron spectra for the H2S molecule.

High-resolution Auger electron spectra of HBr and DBr are presented Extensive vibrational structure has been resolved in the bands corresponding to the 6σ 2 3π 2 final state electron configuration An isotope effect is observed in all the bands A Franck-Condon analysis of the potential curves for the 3d core ionized state and the 3π 2 3 Σ − , 3π 2 1 Δ and 3π 2 1 1Σ + states has been p giving equilibrium bond distances of 153, 166, 169 and 176 A, respectively An approximately linear correlation is found between the equilibrium bond distances and the 0–1 vibrational spacings in HBr, HBr + (3π −1 ) and the different electronic states of HBr 2+ (3π −2 ) The adiabatic electron binding energies for the doubly ionized molecule with π −2 configuration are determined to be 3287, 3397 and 3527 eV for the 3Σ − , 1 Δ and 1 Σ + states, respectively

Isotope effects in the auger electron spectra of HBr and DBr

The electron-impact excited high-resolution {ital L}{sub 2,3}VV Auger-electron spectra of HCl and DCl are presented. Four narrow bands are discerned that show a rich fine structure. Comparison between the HCl and DCl spectra shows this fine structure to be due to transitions to vibrational sublevels in the (2{pi}{sup {minus}2}){sup 3}{Sigma}{sup {minus}}, (2{pi}{sup {minus}2}){sup 1}{Delta}, and (2{pi}{sup {minus}2}){sup 1}{Sigma}{sup +} states of the doubly ionized molecule. By a Franck-Condon analysis the potential curves for all these doubly ionized states in the 2{pi}{sup {minus}2} configuration have been determined. The adiabatic double-ionization energies for the (2{pi}{sup {minus}2}){sup 3}{Sigma}{sup {minus}}, (2{pi}{sup {minus}2}){sup 1}{Delta}, and (2{pi}{sup {minus}2}){sup 1}{Sigma}{sup +} states were determined to be 35.68(5), 37.30(9), and 38.45(10) eV, respectively. The potential well is shallower than 1 eV for all these states, and dissociation occurs via a Coulomb-potential mechanism. The double-ionization energies are used to assign a number of lines in the x-ray-excited photoelectron spectrum of HCl.

M.P. Keane

Papers

Experimental and theoretical XPS study of model molecules for poly(methyl methacrylate)

Experimental and theoretical study of the N1s and C1s shake-up satellites in pyridine and aniline

Observation of an energy shift in the S2p3/2-S2p1/2 spin-orbit splitting between x-ray photoelectron and Auger-electron spectra for the H2S molecule.

Isotope effects in the auger electron spectra of HBr and DBr

High-resolution Auger-electron spectrum of HCl and DCl.