XPS Spectra of organometallic phenyl compounds of P,As, Sb and Bi

XPS spectra of 54 organometallic compounds of group V elements with various coordinations are measured in the solid state. Core level binding energy data for the various atoms present in the molecules are given.     

The sign of Fe3+OCr3+ superexchange determined from Fe57 hyperfine field measurements

The sign of the super-transferred hyperfine field at an impurity site is shown to depend on the sign of the impurity-host superexchange interaction. This fact is used to determine that the Fe³⁺OCr³⁺ superexchange in YCrO₃ is antiferromagnetic.     

Determination of an opiate pentapeptide by on-line reversed phase preconcentration and ligand exchange chromatography with spectrofluorometric detection

Summary In order to study the occurrence of the opiate pentapeptide -[D-Ala^2,4, Tyr⁵] CM-5-NH₂ in the 10^–9–10^–5 M concentration range, we have developed a new method consisting of extraction of the peptide from its buffered aqueous medium onto a reversed phase cartridge of 50 L void volume, followed by on-line injection onto a Cu(II) modified silica gel column. The acetonitrile-rich mobile phase allows detection of the natural fluorescence of the peptide at the picomole level.     

Electronic structure of lithium graphite

X-ray photoemission spectra of vacuum cleaved LiC₆, prepared from highly oriented pyrolytic graphite, provide a direct measure of the filling of the graphite π bands by electrons from Li. The resulting Fermi energy shift is in agreement with recent band structure calculations and indicates near unity charge transfer from Li. Core level spectra exhibit shifts compatible with the expected charge transger and line shapes showing strong asymmetries resulting from the metallic character of this compound.     

A test of factorization methods in coupled channel reaction theory

Factorization methods used in shell-model approaches to nuclear reactions provide a good starting point for perturbative treatments of direct coupling. General algebraic equations are given for zero and higher orders. Problems of convergence of the Born series are tested with a soluble model. It is shown that the zero-order approximation is quite good. First- and second-order corrections are calculated and exhibit a rapid convergence. The influence of parameters entering in factorization formulae is discussed.     

Linear-chain ferromagnetism in the one-dimensional compounds CoCl2(pyrazole)2 and CoCl2(indazole)2

Two linear-chain compounds of formula CoCl₂L₂, with L = pyrazole (pz) and indazole (indz), have been investigated with the aid of IR, far-IR, ligand field and ESR spectra. Magnetic susceptibility data have been collected in the temperature region 4.2–80 K. Analysis of the susceptibility data in terms of the Ising model yielded the values of the ferromagnetic intrachain exchange constants J = 7.2(6) and 7.4(9) cm^-1 for the pz and indz compound, with corresponding g-values of g∥ = 7.9(7), g⊥ = 4.6(9) and g∥ = 10.8(9), g⊥ = 3(1), respectively. The results are discussed and compared with the similar compound CoCl₂(pyridine)₂. The influence of the bridge geometry and of the π-bonding properties of the organic ligands on the exchange constant are considered for the explanation of different J-values. It is suggested that the π-bonding properties of the organic ligand influence the magnitude of the superexchange constant to a great extent.     

13C?1H spin–spin couplings in cyclic α,β-unsaturated enones and their protonated derivatives. Measurements and quantum chemical calculations

Direct and long-range ¹³C? ¹H coupling constants are presented for the enone moieties of cyclopent-2-enone, cyclohex-2-enone and their protonated derivatives. A correlation is given between the experimental values and the results of quantum chemical calculations (CNDO/2, INDO). The existing calculations are modified in order to improve the relationship between the calculated and experimental results.