The Al K alpha, 1486.6 eV, based x-ray photoelectron spectroscopy (XPS) of Fe 2p and 3p for Fe(III) in Fe2O3 Fe(II) FeO is compared with theoretical predictions on ab initio wavefunctions that accurately treat the final, core-hole, multiplets. principal objectives this comparison are to understand multiplet structure evaluate use both spectra determining oxidation states. In order properly interpret features these XPS provide atomistic insights as well atomic composition, it necessary origin...

The origin and assignment of the complex main satellite X-ray photoelectron spectroscopy (XPS) features cations in ionic compounds have been subject extensive theoretical studies using different methods. There is agreement that within a molecular orbital model, one needs to take into account types configurations. Specifically, those where core electron removed, but no other configuration changes are made addition ionization, there also shake or charge-transfer configuration. However, strong...

We present a perspective on the use of XPS relative peak intensities for determining composition in homogeneous bulk materials. Nonhomogenous effects, such as variation with depth or severe topography effects (e.g., nanoparticles), are not discussed. consider only conventional laboratory-based instruments x-ray sources, Alkα Mgkα. address accuracy (not precision, which is much more straightforward) using sensitivity factors, RSFs, obtained either empirically from standards (e-RSF)...

Although the origin and assignment of complex XPS features cations in ionic compounds has been subject extensive theoretical work, agreement with experimental observations remains insufficient for unambiguous interpretation. This paper presents a rigorous ab initio treatment main satellite Fe 2p Fe2O3. possible using unique methodology selection orbitals that are used to form wavefunctions. orbital makes it treat both angular momentum coupling open shell core valence electrons as well shake...

Current day x-ray photoelectron spectroscopy (XPS) instrument makers have made significant advances in charge compensation systems over the last 20 years, which makes it easier to analyze insulators, but samples still many differences chemistry, dielectric properties, sizes, surface roughness, etc. that force operators tweak flood gun settings if they want or need obtain high quality chemical state spectra provide most information. This guide teaches variables check, and how optimize...

The covalent character of the interaction between metal cation and oxygen ligands has been examined for two Fe oxides with different nominal oxidation states, Fe(II)O, Fe(III)2O3. is initial, ground state configuration ionic states involving removal a shallow core, 3p, deep 2p, electron. covalency assessed based on novel theoretical analyses wave functions various cases. It found that considerably ionized non-ionized configurations. changes in ions are shown to be responsible important...

We have examined, for Fe2O3, the three commonly used background removal procedures: Shirley (iterated), S; Tougaard (a modified U2 version), T; and Linear, L, Fe2p O1s spectra. The high BE end point, which is where it assumed that there no further intrinsic signal contribution, most important. It quite easy, but arbitrary, to adjust points return an “expected” answer 40% atomic Fe, while assuming 100% accuracy cross sections inelastic mean free path length parameters O1s. This assumes (a)...

Although precision in XPS can be excellent, allowing small changes to easily observed, obtaining an accurate absolute elemental composition of a solid material from relative peak intensities is generally much more problematical, involving many factors such as background removal, differing analysis depths at different photoelectron kinetic energies, possible angular distribution effects, calibration the instrument transmission function, and variations intensity between “main” peaks (those...

This paper addresses the challenges of fitting asymmetric photoelectron peaks by showing that use double Lorentzian (DL) line shape usually leads to high-quality, reliable, and reproducible fits. In contrast Doniach-Sunjic (DS) shape, used fit peaks, DL distribution is integrable produces higher-quality The functional form described in detail; examples application DS transition metals one metal oxide are shown. from symmetric Voigt functions, many functions smooth easy. encompassed freely...

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTDissymmetric chromophores. 7. Optical activity of conjugated cisoid dienes: experimental-theoretical study 5-alkyl-1,3-cyclohexadienesDavid A. Lightner, Thomas D. Bouman, Jacek K. Gawronski, Krystyna Gawronska, Jacques L. Chappuis, B. Vincent Crist, and Aage E. HansenCite this: J. Am. Chem. Soc. 1981, 103, 18, 5314–5327Publication Date (Print):September 1, 1981Publication History Published online1 May 2002Published inissue 1 September...

XPS analyses of open shell ionic compounds, especially oxides the first row transition metals, for information such as oxidation state tend to focus on characteristics metal 2p features alone. These could be made considerably more robust with simultaneous characterization 3p well features. In these comments, we provide a perspective conceptual and theoretical framework needed extract chemical from complex multiplet structure Fe representative 3d oxides. We also present about novel kind...

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTSterols of marine invertebrates. 44. Isolation, structure elucidation, partial synthesis, and determination absolute configuration pulchrasterol. The first example double bioalkylation the sterol side chain at position 26B. Vincent Crist, Xian Li, Patricia R. Bergquist, Carl DjerassiCite this: J. Org. Chem. 1983, 48, 24, 4472–4479Publication Date (Print):December 1, 1983Publication History Published online1 May 2002Published inissue 1 December...

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTThe octant rule. 15. Antioctant effects: synthesis and circular dichroism of 2-exo- 2-endo-alkylbicyclo[2.2.1]heptan-7-ones bicyclo[3.2.1]octan-8-onesDavid A. Lightner, B. Vincent Crist, Nagabushanam Kalyanam, Leslie M. May, Dennis E. JackmanCite this: J. Org. Chem. 1985, 50, 20, 3867–3878Publication Date (Print):October 1, 1985Publication History Published online1 May 2002Published inissue 1 October...

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTThe Octant Rule. 21. Circular dichroism dependence on .alpha.-methyl configuration in cyclohexanones. Experiments and RPA calculationsDavid A. Lightner, Thomas D. Bouman, B. Vincent Crist, Stephen L. Rodgers, Michael Knobeloch, Aaron M. JonesCite this: J. Am. Chem. Soc. 1987, 109, 21, 6248–6259Publication Date (Print):October 1, 1987Publication History Published online1 May 2002Published inissue 1 October...

Conformational analysis of 3-methylcyclohexanone assumed a special importance some time ago in connection with the so-named 3-alkylketone effect. Klyne and Robins Walker noted that axial conformation one 1,3-diaxial H:CH3 interactions methylcyclohexane was missing concluded conformational energy difference between equatorial methyl forms should be lowered from value 7.11 kJ/mol (for methylcyclohexane) to one-half value, or 3.55 kJ/mol. The (3.55 kJ/mol) A-values is called In order generate...

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTDissymmetric chromophores. 5. Synthesis and circular dichroism of chiral 3-methylenebicyclo[2.2.1]heptan-2-onesDavid A. Lightner, Michael J. Flores, B. Vincent Crist, Jacek K. GawronskiCite this: Org. Chem. 1980, 45, 17, 3518–3522Publication Date (Print):August 1, 1980Publication History Published online1 May 2002Published inissue 1 August 1980https://pubs.acs.org/doi/10.1021/jo01305a033https://doi.org/10.1021/jo01305a033research-articleACS...

The relative intensities of XPS core levels, scaled by their photoionization cross sections, are regularly used to determine sample atomic composition. Cross however, give the intensity all possible final states for ionizations, not just main peak. This includes intrinsic satellite structure (shake and, open shell systems, different ionic multiplets). In practice, solids, this is usually experimentally impossible accurately because such a sits on inelastically scattered electron background...