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  • 1
    Electronic Resource
    Electronic Resource
    Differences between L3 and L2 x-ray absorption spectra of transition metal compounds (1994)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 101 (1994), S. 6570-6576 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The differences between L3 and L2 edges of 3d and 4d transition metal complexes and compounds in octahedral symmetry are discussed. The main origin of these differences are the multiplet effects due to the coupling of the 2p core wave function and the 3d and 4d valence wave functions. The 3d and 4d spin–orbit coupling is a second origin of difference. For 3d systems the multiplet effects dominate all other interactions and the L3 and L2 edge are completely mixed and reordered. For 4d systems the core hole spin–orbit coupling is large and the L3 and L2 are separated by about 100 eV with a ratio close to 2:1. The differences between the L3 and L2 edge originate from the weight transfer between the t2g and eg peaks due to the multiplet effect. This weight transfer is about 25% for the L3 edge and about 5% for the L2 edge, which implies that for a comparison to single-particle calculations the L2 edge is preferable to use. Partly filled 4d systems are low-spin and the occupation of the t2g states implies a decrease of the first peak. This decrease is stronger for the L2 edge, implying an increase in the L3:L2 ratio. For 4d5 systems transitions to the t2g hole are only possible at the L3 edge due to the combined effects of 4d spin–orbit coupling and the dd multiplet effects.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.468351
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  • 2
    Electronic Resource
    Electronic Resource
    Solvent effects on the mechanism and selectivities of asymmetric Diels-Alder reactions (1993)
    s.l. : American Chemical Society
    Journal of the American Chemical Society 115 (1993), S. 8780-8787 
    Details
    ISSN: 1520-5126
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/ja00072a035
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  • 3
    Electronic Resource
    Electronic Resource
    Ab Initio Analysis of Water-Assisted Reaction Mechanisms in Amide Hydrolysis (1994)
    s.l. : American Chemical Society
    Journal of the American Chemical Society 116 (1994), S. 3912-3921 
    Details
    ISSN: 1520-5126
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/ja00088a030
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  • 4
    Electronic Resource
    Electronic Resource
    Water dimer in liquid water (1992)
    Springer
    Theoretical chemistry accounts 84 (1992), S. 181-194 
    Details
    ISSN: 1432-2234
    Keywords: Water dimer ; Self-consistent reaction field ; Cooperative phenomenon ; Liquid state ; Water-water potential
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A Self-Consistent Reaction Field Model is used to study the effect of the molecular environment on the electronic distribution and on the equilibrium geometry of the water dimer in liquid water. Computations are performed at the 6-311G++(2d,2p) MP2 level. Comparison of the results for the monomer and the dimer, in a vacuum and in the liquid, is made in order to gain a deeper insight on the cooperative phenomenon. The discussion emphasizes the trends which should be considered for deriving more sophisticated water-water potentials.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01113207
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  • 5
    Electronic Resource
    Electronic Resource
    2-Nitroethanal conformations in solution: AnAb initio SCRF study (1994)
    Springer
    Structural chemistry 5 (1994), S. 357-360 
    Details
    ISSN: 1572-9001
    Keywords: Cavity model ; solvent effect ; ab initio ; 2-nitroethanal
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The structure of 2-nitroethanal has been studied at the MP2/6-31G* level in the gas phase and in acetonitrile using a continuum model to represent the electrostatic solute-solvent interactions. The relative energies of the two stable conformations obtained are quite dependent on the media. Indeed, our computations predict a change of the most stable conformation from gas to polar solvent. These results are in agreement with experimental data for the axial/equatorial conformational equilibrium of 2-nitrocyclohexanone.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02252893
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  • 6
    Electronic Resource
    Electronic Resource
    Resonant photoemission at the 2p thresholds of Fe, Co, and Ni metal (1994)
    Springer
    The European physical journal 95 (1994), S. 9-12 
    Details
    ISSN: 1434-6036
    Keywords: 74.70.Vy ; 78.70.Dm ; 79.60.Eq
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Resonant photoemission studies have been performed at the 2p soft-x-ray absorption thresholds of Fe, Co, and Ni metal. At resonance, the photoelectron intensity exhibits a strong enhancement in the region of the two-hole satellites, which is shown, however, to be mostly due to an incoherent superposition of a photoemission signal with a more intense signal from anL 3 M 4,5 M 4,5 Coster-Kronig decay of the core-ionized state. The resonant enhancement of the valence-band photoemission satellite in Ni metal amounts to a factor of ≃12. In contrast, no photoemission satellites are observed for Fe and Co metal.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01316837
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  • 7
    Electronic Resource
    Electronic Resource
    A multiple-scattering approach to the study of X-ray absorption spectra of anatase and rutile (1993)
    Springer
    Catalysis letters 20 (1993), S. 59-71 
    Details
    ISSN: 1572-879X
    Keywords: EXAFS ; XANES ; TiO2 ; multiple scattering
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Theoretical computations of the X-ray absorption spectra of the crystalline forms of TiO2, rutile and anatase, have been carried out in order to analyze the influence of multiple scattering contributions to the absorption coefficient. The cluster size used in the computations after making a detailed study of shell contributions, has been 75 atoms for rutile and 63 for anatase. This work has been envisaged as a suitable starting point to the analysis of experimental data for the more complicated TiO2 amorphous systems involved in catalytic processes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00772597
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  • 8
    Electronic Resource
    Electronic Resource
    Resonant photoemission in highly localized versus weakly localized solids (1994)
    Springer
    The European physical journal 94 (1994), S. 1-2 
    Details
    ISSN: 1434-6036
    Keywords: 79.60.Cn ; 78.70.Dm
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract We report on comparative study of angle-resolved photoelectron spectra of Ni metal and CeGd at theM III andN IV,V soft-x-ray absorption threshold, respectively. OnM III resonance, the valence-band photoemission (PE) intensity of Ni follows a cos2-behavior, while the intensity of the 6-eV satellite is independent of the angle of emission relative to the E-vector of the incoming beam. On the other hand, the 4f Ce PE signal behaves ∝ cos2 onN IV,V resonance. This clearly shows that the resonant enhancement of the 6-eV PE satellite of Ni is mainly caused by an incoherent Auger decay and cannot be described as a resonant PE process.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01307645
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  • 9
    Electronic Resource
    Electronic Resource
    Experimental and theoretical study of the influence of the solvent on asymmetric diels - alder reactions (1992)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 5 (1992), S. 230-238 
    Details
    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Rate, endo/exo and diastereofacial selectivities of the Diels-Alder reaction between cyclopentadiene and ( - )-menthyl acrylate were measured in a series of organic solvents and organic-aqueous mixtures. Regression analyses show that a model with the α empirical solvent parameter accounts for most of the changes in rates and diastereofacial selectivities, whereas in the case of the endo/exo selectivity, inclusion of the π* and δ parameters is needed. Theoretical calculations carried out on the model reaction between methyl acrylate and cyclopentadiene using dielectric continuum and supermolecule models do not clearly show the effect of the different solvation mechanisms on rate. However, they agree with the above-mentioned influence of α and π* on the endo/exo and diastereofacial selectivities.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/poc.610050503
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  • 10
    Electronic Resource
    Electronic Resource
    A density functional study of pseudotetrahedral metal-nitrosyl complexes (1994)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 52 (1994), S. 1039-1049 
    Details
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Local and nonlocal density functional computations have been carried out to study the electronic structure and the equilibrium geometry of the isoelectronic series Cr(NC)4, Mn(NO)3(CO), Fe(NO)2(CO)2, and Co(NO)(CO)3 and model compounds Fe(NO)2L2 (L = Cl, HCN, NH3, PH3, and C2H4). The structure of Fe(NO)2(C4H6) is also described. The discussion is focused on structural modifications through a change of ligand, in particular those concerning the metal-nitrosyl conformation (linear vs. bent). Though this is a preliminary study of metal-nitrosyl properties by DFT methods and more computations are required to analyze the mechanism of homogeneous catalysis processes, our results support the hypothesis that structural reorganization from linear to bent metal-nitrosyl plays a key role in some reactions, such as in butadiene dimerization. © 1994 John Wiley & Sons, Inc.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560520429
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