Core-level binding-energy shifts at surfaces and in solids

X-ray absorption and dichroism of transition metals and their compounds

http://w0.rz-berlin.mpg.de/hjfdb/pdf/110e.pdf

Formation of a well-ordered aluminium oxide overlayer by oxidation of NiAl(110)

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.

Branching ratio in x-ray absorption-spectroscopy

The electron energy loss and X-ray absorption spectra of two phases of titanium dioxide-rutile and anatase-are reported. Although the nearest-neighbour environments of titanium and oxygen in both these structures are very similar, noticeable differences are observed between the electron energy loss and the X-ray absorption spectra. Attempts to model these differences using real-space multiple-scattering calculations are reasonably successful at the Ti K and O K edges. The authors propose an interpretation of the Ti L2.3 edge, notably for the presence of a previously unobserved splitting on the L3 edge.

https://iopscience.iop.org/article/10.1088/0953-8984/1/4/012/pdf

Electron energy loss and X-ray absorption spectroscopy of rutile and anatase: a test of structural sensitivity

Surface shifts on rare earth metals

4f-surface binding energy shift for Eu and Gd metals

The core-level binding-energy shifts for surface atoms relative to bulk atoms ("surface shifts") have been measured for the $2p$ levels of Na (220 meV) and Mg (140 meV) using synchrotron-radiation-excited photoelectron spectroscopy. For Al, both a surface shift and a broadening are considered. The sign and magnitude of these shifts are compared with calculated values based on surface energies. The mean free path of the photoelectrons is determined by evaluation of the intensity ratio $\frac{{I}_{\mathrm{bulk}}(2p)}{{I}_{\mathrm{surface}}(2p)}$.

/pdf/surface-binding-energy-shifts-for-sodium-magnesium-and-31nheg4n3v.pdf

Surface-binding-energy shifts for sodium, magnesium, and aluminum metals

The photoionization cross section of the 3d valence band is obtained for Ca through Cr in the photon-energy range between 15 and 150 eV. Strong interference-like resonances are observed in the region of the 3p threshold. The resonances show a double structure probably due to shakeup effects.

/pdf/experimental-study-of-the-3p-3d-intershell-interaction-in-ca-1ew79t4q29.pdf

Experimental study of the 3p-3d intershell interaction in Ca, Sc, Ti, V, and Cr metals

The oxidation-induced valence change of Yb leads to a single $4f$ hole in the ground state. The creation of the $4{f}^{13}$ configuration which does not exist for any pure rare-earth metal makes it possible to analyze the $4d\ensuremath{\rightarrow}4f$ Fano resonance for a simple system experimentally as well as theoretically. Calculated Fano profiles for the $4{f}^{12}$ final-state multiplets are in good agreement with photoemission measurements taken with the FLIPPER monochromator at Hamburger Synchrotron-strahlungslabor, Deutsches Elektronen-Synchrotron, using synchrotron radiation from the storage ring DORIS.

F. Gerken

Papers

Surface shifts on rare earth metals

4f-surface binding energy shift for Eu and Gd metals

Surface-binding-energy shifts for sodium, magnesium, and aluminum metals

Experimental study of the 3p-3d intershell interaction in Ca, Sc, Ti, V, and Cr metals

Resonant photoemission of oxidized Yb: Experiment and theory