Muffin-tin model without constructing a potential: determination of atomic phaseshifts from experiment

Migal, Yu. F.

doi:10.1088/0953-4075/32/19/302

Cited by 4 publications

(3 citation statements)

References 12 publications

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“…Our task is to reveal these parameters. From our previous studies (Migal, 1999) it follows that just characteristics of atomic valence states can be such parameters.…”

Section: Problemmentioning

confidence: 95%

“…where f l is a notation for F l with starting values of the parameters ε b and <r> b , ϕ l and χ l are some auxiliary functions independent of these parameters (see Migal, 1999). Coefficients c l and d l are new variables determined through minimizing functional (3).…”

Section: Parameters Of Potential Determined By Xanesmentioning

confidence: 99%

“…Equation (4) is employed within an algorithm worked out for determining parameters ε b and <r> b . Details of this algorithm are described in (Migal, 1999)…”

Section: Parameters Of Potential Determined By Xanesmentioning

confidence: 99%

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Determination of parameters of valence states by using XANES

Migal

Kovaleva

2001

J Synchrotron Radiat

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A new approach for the parametrization of valence states of atoms in molecules and solids, facilitating the deciphering of experimental XANES spectra, is proposed. It is shown that energies and halfwidths of XANES maxima of the one-electron origin depend mainly on the arrangement of atoms and energies and mean radii of atomic valence states. Just these quantities having distinct physical meaning must be determined above all from experiment. A procedure for such a determination is developed. Values of energies and mean radii of the nitrogen and oxygen atoms in some molecules are obtained. Keywords: XANES, valence states ProblemOur aim is to investigate valence states of separate atoms in manyatom systems. Such systems can be molecules, free or adsorbed, solid clusters and so on. This problem is a part of the more general question which we try to examine (Migal, 1994): what information about objects under consideration is contained in XANES and how to extract this information.Analysing XANES we choose peaks of the one-electron origin. As usual such peaks are the most distinctive details of spectra. They correspond to the transition of the photoelectron to both unoccupied collective states of the discrete spectrum and so called shape resonances. The latter are one-electron quasi-stationary states with small positive energies. We consider only such peaks which correspond to states localized or quasi-localized within many-atom systems (i.e., the Rydberg series is excepted). Position and form of these peaks essentially depend on arrangements and types of atoms, magnetic microstructure, the presence and nature of defects, the distribution of electric charge, etc. This fact allows us, in principle, to obtain structure information by analysing characteristics of the peaks. However, unfortunately, general methods for extracting this information are still not developed.Before considering concrete questions about atomic valence states we would like to make three general remarks. Firstly, an amount of information coded in XANES is essentially greater than in EXAFS. It is caused by the fact that in the case of XANES the photoelectron, moving through a many-atom system with a comparatively small speed, interacts with the system for much longer time than in the case of EXAFS. Due to that, by using XANES it is possible to obtain, along with geometric parameters of the system, also parameters of the potential V(r) describing the interaction between the photoelectron and the system. Secondly, since position and form of peaks in XANES depend on a lot of factors, in order to extract information from XANES one must solve a many-parameter inverse problem. In a number of works, where for deciphering structure information from XANES

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“…Our task is to reveal these parameters. From our previous studies (Migal, 1999) it follows that just characteristics of atomic valence states can be such parameters.…”

Section: Problemmentioning

confidence: 95%

Section: Parameters Of Potential Determined By Xanesmentioning

confidence: 99%

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Determination of parameters of valence states by using XANES

Migal

Kovaleva

2001

J Synchrotron Radiat

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Migal

Kovaleva

2001

Journal of Structural Chemistry

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A comprehensive photoabsorption, photoionization, and shake-up excitation study of the C 1s cross section of benzene

Rennie

Kempgens

Köppe

et al. 2000

The Journal of Chemical Physics

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The absolute photoabsorption cross section of benzene (C6H6), encompassing the C 1s−1 π*e2u resonance, the C 1s threshold, the satellite thresholds, and extending up to 800 eV, has been measured using synchrotron radiation. Measurements of the discrete absorption structure from below the C 1s ionization threshold have been performed at high resolution. In order to unambiguously assign all structure present in the photoabsorption cross section, C 1s photoelectron spectra were measured from the C 1s threshold region up to 350 eV along with satellite spectra. The C 1s−1 single-hole and the satellite cross sections have been derived in absolute units, and their angular distributions have been determined. Resonant and normal Auger spectra were taken on the main features of the photoabsorption and single-hole cross sections. From the best resolved photoelectron spectra the underlying structure in the asymmetric benzene photoelectron peak can be partly disentangled. The experimental data show that at least two vibrational modes play a role in the C 1s photoelectron spectrum. The behavior of the investigated shake-up structure closely resembles that of ethene and ethyne, where the satellite bands due to π→π* excitations gain intensity towards threshold, an observation which may be attributed to conjugate shake-up processes. These processes lead to a significant contribution of the satellite intensity to the production of the absorption features traditionally assigned to the carbon shape resonances in benzene. An EXAFS analysis of the wide range oscillations present on the photoabsorption cross section has been performed, and reveals the C–C nearest-neighbor distance.

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Muffin-tin model without constructing a potential: determination of atomic phaseshifts from experiment

Cited by 4 publications

References 12 publications

Determination of parameters of valence states by using XANES

Determination of parameters of valence states by using XANES

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A comprehensive photoabsorption, photoionization, and shake-up excitation study of the C 1s cross section of benzene

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