Core-electron line shapes in x-ray photoemission spectra from semimetals and semiconductors

Circularly polarized x-ray radiation is attracting increasing interest as a tool for the characterization of the electronic, magnetic, and chiral properties of low-dimensional structures. Using circular light (with electric field vector parallel to the orbital plane), a dependence of the measured quantity by changing either the orientation of the light polarization or the magnetization is indicative of the existence of magnetic circular dichroism. It can be observed in x-ray absorption spectroscopy (XAS), in which the photon energy is scanned through an absorption threshold exciting a core electron into an unoccupied valence state using circularly polarized light. Synchrotron radiation sources have made this technique possible. It can also be observed in photo-emission spectroscopy from core and valence levels. Here we focus on magnetic circular x-ray dichroism (MCXD) in XAS as an element-specific tool to investigate magnetic properties of ultrathin films in situ. The application of magneto-optical sum rules enables the determination of the orbital and spin magnetic moments per atom from XAS spectra, as well as the easy magnetization direction.MCXD-based magnetometry in XAS is extensively used by measuring the L absorption edges of 3d-transition metals, where large intensity changes (up to 60%) of the L-edge white lines are observed upon reversal of either the sample magnetization or the light helicity. The high magnetic contrast obtained, combined with the elemental specificity of the technique, allows for the study of very dilute samples such as ultrathin films. We first concentrate on the selection rules governing MCXD in XAS.

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Measuring the supermassive black hole parameters with space missions

Proceedings of the International Astronomical Union ◽

10.1017/s1743921307006023 ◽

2006 ◽

Vol 2 (S238) ◽

pp. 475-476

Author(s):

Alexander F. Zakharov

Keyword(s):

Black Hole ◽

Spectral Line ◽

Accretion Disks ◽

Seyfert Galaxies ◽

Emission Lines ◽

X Ray ◽

Line Shapes ◽

Supermassive Black Hole ◽

Broad Emission ◽

Different Types

AbstractRecent X-ray observations of microquasars and Seyfert galaxies reveal broad emission lines in their spectra, which can arise in the innermost parts of accretion disks. Recently Müller & Camenzind (2004) classified different types of spectral line shapes and described their origin. Zakharov (2006b) clarified their conclusions about an origin of doubled peaked and double horned line shapes in the framework of a radiating annulus model and discussed s possibility to evaluate black hole parameters analyzing spectral line shapes.

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Potentialities of an Innovative Technique Like 129Xe NMR and of Saxs for the Characterization of Microporous Sol-Gel Derived SiO2

MRS Proceedings ◽

10.1557/proc-431-159 ◽

1996 ◽

Vol 431 ◽

Author(s):

L. C. de Menorval ◽

A. Julbe ◽

H. Jobic ◽

J. A. Dalmon ◽

C. Guizard

Keyword(s):

Chemical Shifts ◽

High Surface ◽

Sol Gel ◽

Narrow Pore Size Distribution ◽

X Ray ◽

Porous Texture ◽

129Xe Nmr ◽

Line Shapes ◽

X Ray Scattering

AbstractAddition of surfactants in TEOS derived sols leads to micro- or mesoporous materials whose porous texture can be varied by changing the surfactant quantity and/or chain length. This series of materials, with a relatively narrow pore size distribution, is well adapted to study the potentialities of an innovative characterization technique like 129Xe Nuclear Magnetic Resonance in comparison with Small Angle X-ray Scattering and N2 adsorption. SAXS revealed a high surface rugosity of the materials and a good correlation with pore hydraulic radius distributions measured by N2 adsorption. Using 129Xe NMR, we have studied the Xe chemical shifts (δXe,) as a function of pXe, and have pointed out several original results showing the importance, for microporous materials, of the NMR line shapes and of the slope of the lines δXe.=f(pXe).

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Following excited-state chemical shifts in molecular ultrafast x-ray photoelectron spectroscopy

Nature Communications ◽

10.1038/s41467-021-27908-y ◽

2022 ◽

Vol 13 (1) ◽

Author(s):

D. Mayer ◽

F. Lever ◽

D. Picconi ◽

J. Metje ◽

S. Alisauskas ◽

...

Keyword(s):

Excited State ◽

Chemical Shift ◽

Photoelectron Spectroscopy ◽

Chemical Shifts ◽

Excited Molecule ◽

Charge Motion ◽

Core Electron ◽

Xps Spectra ◽

X Ray ◽

State Chemical

AbstractThe conversion of photon energy into other energetic forms in molecules is accompanied by charge moving on ultrafast timescales. We directly observe the charge motion at a specific site in an electronically excited molecule using time-resolved x-ray photoelectron spectroscopy (TR-XPS). We extend the concept of static chemical shift from conventional XPS by the excited-state chemical shift (ESCS), which is connected to the charge in the framework of a potential model. This allows us to invert TR-XPS spectra to the dynamic charge at a specific atom. We demonstrate the power of TR-XPS by using sulphur 2p-core-electron-emission probing to study the UV-excited dynamics of 2-thiouracil. The method allows us to discover that a major part of the population relaxes to the molecular ground state within 220–250 fs. In addition, a 250-fs oscillation, visible in the kinetic energy of the TR-XPS, reveals a coherent exchange of population among electronic states.

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Fermi surface excitations in X-ray photoemission line shapes from metals

Topics in Applied Physics - Photoemission in Solids I ◽

10.1007/3540086854_5 ◽

1978 ◽

pp. 197-236 ◽

Cited By ~ 49

Author(s):

G. K. Wertheim ◽

P. H. Citrin

Keyword(s):

Fermi Surface ◽

X Ray ◽

Line Shapes

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Determination of the oxidation state of manganese in lepidolite by X-ray photoelectron spectroscopy

Clay Minerals ◽

10.1180/claymin.1982.017.4.11 ◽

1982 ◽

Vol 17 (4) ◽

pp. 477-481 ◽

Cited By ~ 10

Author(s):

S. Evans ◽

E. Raftery

Keyword(s):

Oxidation State ◽

Photoelectron Spectroscopy ◽

Electronic Spectroscopy ◽

Binding Energies ◽

Core Electron ◽

X Ray ◽

Occasional Occurrence ◽

The Subject ◽

Electron Binding Energies

It is usually assumed that the oxidation state of the small proportion of Mn sometimes present in micas is +2, although there is evidence from electronic spectroscopy (Burns, 1970) for at least the occasional occurrence of Mn(III) in manganophyllite. We describe here X-ray photoelectron spectroscopic (XPS) measurements on the Mn in a Norwegian lepidolite which was the subject of a concurrent structural study by X-ray photoelectron diffraction (Evans & Raftery, 1982). To establish the Mn oxidation state we have compared the Mn2p core-electron binding energies (BE), the Mn2P3/2-O ls BE differences, and the Mn2p XPS peak profiles from the four common oxides of manganese (MnO, Mn3O4, Mn2O3 and MnO2) with those from the lepidolite. A re-examination of these oxides was undertaken because the agreement between reports in the literature was unsatisfactory, and uncertainty existed concerning the integrity of some of the surfaces previously examined.

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