A new magneto-optical sum rule is derived for circular magnetic dichroism in the x-ray region (CMXD). The integral of the CMXD signal over a given edge allows one to determine the ground-state expectation value of the orbital angular momentum. Applications are discussed to transition-metal and rare-earth magnetic systems.

A critical review of the kinetics and selectivity of the Fischer–Tropsch synthesis (FTS) is given. The focus is on reaction mechanisms and kinetics of the water–gas shift and Fischer–Tropsch (FT) reactions. New developments in the product selectivity as well as the overall kinetics are reviewed. It is concluded that the development of rate equations for the FTS should be based on realistic mechanistic schemes. Qualitatively, there is agreement that the product distribution is affected by the occurrence of secondary reactions (hydrogenation, isomerization, reinsertion, and hydrogenolysis). At high CO and H2O pressures, the most important secondary reaction is readsorption of olefins, resulting in initiation of chain growth processes. Secondary hydrogenation of α-olefins may occur and depends on the catalytic system and the process conditions. The rates of the secondary reactions increase exponentially with chain length. Much controversy exists about whether these chain-length dependencies stem from differe...

The satellite structure of core photoelectron and Auger lines of the copper dihalides are explained in terms of final-state energies diminished by Coulomb interactions between the valence electrons and the created core hole or holes. The satellite structure in the $3p$ and valence-band photoelectron spectra are shown to originate from the same final states as the $L_3{M}_{23}{M}_{45}$ and $L_3{M}_{45}{M}_{45}$ main Auger lines. The energies of the main core lines are shown to yield information about the valence ligand binding energies and therefore are sensitive to chemical shifts. The satellite lines are rather insensitive to chemical shifts but their intensities yield information concerning the relative positions of the Cu $3d$ and ligand valence holes and the amount of hybridization. In terms of the core line photoelectron and Auger spectra we show that an assignment can be made of the valence-band spectra. From a combination of all the results we conclude that especially Cu${\mathrm{Cl}}_2$ and Cu${\mathrm{Br}}_2$ are strongly covalent and we predict that in Cu${\mathrm{I}}_2$ the valence hole would be predominantly in the I $5p$ level which is probably the reason why this material is not stable.

We have measured and calculated the 3d ($M_4$,5) absorption spectra for all the rare-earth metals, as well as the full 3$d^9$4$f^{n+1\mathrm{}}$ multiplets for the early and late rare earths. The quality of agreement between theory and experiment is excellent, except for Sm. In x-ray-absorption spectroscopy (XAS), only dipole selected lines are seen but all multiplet effects can be observed in x-ray photoemission spectroscopy. The line shapes and 3d-4f interactions are discussed. Our results provide an improved basis for use of the 3d XAS spectra for studies of ‘‘mixed-valence’’ systems.

The origin of nonstatistical branching ratios in spin-orbit-split x-ray absorption spectra is explained. Atomic calculations for transition metals show a systematic change which is due to initial-state spin-orbit splitting and electrostatic interactions between core hole and valence electrons. We have formulated the results of these atomic calculations in general rules, which are also applicable to solids. In the free atom the branching ratio reaches a maximum for the Hund’s-rule ground state and its value decreases gradually for S, L, and J levels of higher energy. The presence of a crystal field results in a lower branching ratio when it produces a low-spin ground state. The rules can be used to assess the spin state and the spin-orbit splitting from the experimental branching ratio in transition-metal and rare-earth compounds. A specific example is given for the influence of second-order spin-orbit interactions in high-spin Ni compounds.