A microspectroscopic study of the electronic homogeneity of ordered and disordered Sr2FeMoO6

Disordered Sr₂FeMoO₆ shows a drastic reduction in saturation magnetization compared to highly ordered samples, moreover magnetization as a function of the temperature for different disordered samples shows qualitatively different behaviours. We investigate the origin of such diversity by performing spatially resolved photoemission spectroscopy on various disordered samples. Our results establish that e_xtensive electronic inhomogeneity, arising most probably from an underlying chemical inhomogeneity in disordered samples, is responsible for the observed magnetic inhomogeneity. It is further pointed out that these inhomogeneities are connected with composition fluctuations of the type Sr₂Fe_1+x Mo_1-x O₆ with Fe-rich (x > 0) and Mo-rich (x < 0) regions. Dedicated to Prof J Gopalakrishnan on his 62nd birthday.     

Nonfactorization and the decaysD s +→φπ +,φρ + andφl + ν l

Using the experimentally measured values ofx=A ₂(0)/A ₁(0) andy=V(0)/A ₁(0) and the measured ratiosR _st=Γ(D _s ⁺ →φl ⁺ ν _l)/Γ(D _ins ⁺ →φπ ⁺) andR _h=Γ(D _s ⁺ →φρ ⁺)/Γ(D _s ⁺ →φπ ⁺), we present evidence for significant nonfactorization contribution in the decay amplitude forD _s ⁺ →φπ ⁺. We analyze the role of nonfactorization inD _s ⁺ →φρ ⁺ and conclude that present data onR _h are consistent with factorization inD _s ⁺ →φρ ⁺. A measurement of polarization inD _s ⁺ →φρ ⁺ would greatly assist our analysis.     

Molecular constants of substituted ethylene-type molecules: IV. Inertia defects and rotational constants of vinyl halides and their deuterated derivatives

The inertia defects of some vinyl halides and their deuterated derivatives have been calculated on the basis of the general formulation developed by Oka and Morino. The initial sets of Urey-Bradley force constants, based on published data, were adjusted by a least squares procedure until they reproduced the fundamental vibrational frequencies satisfactorily. The Coriolis coupling constants which satisfy the sum rules derived were evaluated and used to calculate the inertia defect in the ground vibrational state. The theoretical values of the inertia defect are used to determine the rotational constant A which cannot otherwise be accurately determined from an “a” type transition.     

On a new partitioning of the Hamiltonian in many-body calculation of pair-correlation energies in closed-shell systems

We introduce here a new partitioning of the Hamiltonian in calculating pair-correlation energies using many-body perturbation theory, by which we are able to eliminate the off-diagonal particle–hole (p–h) ladders exactly to all orders in the perturbation expansion. In this formulation, the particle states turn out to be different for each distinct pair of hole states in the correlation energy calculation. We have also included the contributions of the diagonal particle–particle (p–p) and hole–hole ladders exactly to all orders. The effect of the off-diagonal p–p ladders has been estimated for each pair by computing the third-, foruth- and fifth-order energies. For highly symmetric systems the present partitioning yields in general symmetry-broken orbitals. Here one may use an average kind of partitioning for all the partners of the degenerate sets, which restores the symmetry and at the same time ensures cancellation of the p–h ladders exactly at the lowest order and approximately at the higher orders. Results are presented for a selection of 6π-electron conjugated systems. The correlation energy for each pair is in excellent agreement with that obtained from a partial CI calculation involving all double excitations from this pair. The advantages of implementing the present scheme in larger systems has been discussed.     

Synthetische Versuche in der Gruppe hypotensiv wirksamer Alkaloide, 13. Mitt.: Synthese vondl-10-Methyldeserpidin,dl-10-Äthoxydeserpidin unddl-10-Methylmercapto-deserpidin

Zusammenfassung Die durch Umsetzung von 5-Methyltryptamin, 5-Äthoxytryptamin und 5-Methylmercapto-tryptamin (I, R=CH₃, OC₂H₅ bzw. SCH₃) mit dem racemischen Aldehyd-Ester II entstandenenSchiffschen Basen wurden durch Natriumborhydrid-Reduktion in Methanol unter gleichzeitiger Cyclisierung und Desacetylierung in die entsprechenden 10-substituiertendl-Methyl-2,3-seco-3-oxodeserpidate (IV) übergeführt. Die bei der Einwirkung von 3,4,5-Trimethoxybenzoylchlorid in Pyridin erhaltenen Ester V wurden weiter mit Phosphoroxychlorid cyclisiert und die Produkte als Perchlorate (VI) mit Zink in sauerer Lösung zu den entsprechenden 10-substituiertendl-Deserpidinen (VII, R=CH₃, OC₂H₅ bzw. SCH₃) reduziert. Mit Hilfe der Chromatographie gelang es in zwei Fällen, aus den Rohprodukten auch die entsprechendendl-3-Isodeserpidine (VIII, R=CH₃ bzw. OC₂H₅) zu isolieren. Zum Unterscheiden der Produkte der normalen Reihe (VII) und der 3-Iso-Reihe (VIII) wurden IR-Spektren und die Papierchromatographie angewendet.Mit 2 Abbildungen     

Stokes/anti-stokes intensity ratio in the resonance region

Relative intensities of the Stokes and anti-Stokes Raman lines associated with the I-I stretching mode of I₂ and symmetric stretching mode of MnO^?₄ are presented. The data indicate that the maxima in the excitation profile of the anti-Stokes scattering are shifted from those of the Stokes scattering. The experimental Stokes/anti-Stokes intensity ratios agree with the theoretical values obtained with parameters from the electronic absorption spectra.     

On the characterization of electrified interface

Summary Estimation of zeta potential from experimental data on electroosmotic and electrophoretic effects for Zeokarb 225 (Na⁺ form)/methanol-water system has been made and discussed. Results indicate that zeta potentials estimated from electroosmotic flux and electrophoretic mobility are not in agreement and vary with applied potential difference in a linear manner. Reasons for the variation of zeta potential with electrical field have been discussed. It has been argued that zeta potentials estimated from electroosmotic data are more reliable in comparison to the values obtained from electrophoretic data.With 2 figures and 2 tables