On the hyperfine structure of paramagnetic resonance: the s -electron effect

1955 ◽  
Vol 230 (1181) ◽  
pp. 169-187 ◽  
Keyword(s):  
Neutral Atoms ◽  
Transition Elements ◽  
Paramagnetic Resonance ◽  
Electron Effect ◽  
Hartree Fock ◽  
Full Explanation ◽  
Unpaired Spin ◽  
Paramagnetic Ions ◽  
The Right ◽  
Open Question

Unpaired s -electrons play an important part in hyperfine spectra, even when the nominal spectroscopic configuration contains no unpaired s -electrons. This situation occurs in paramagnetic resonance and optical spectra. A survey of the experimental evidence for the effect is given in relation to the paramagnetic ions and the neutral atoms of the 3 d transition elements. It appears that the central density of unpaired spin is nearly the same in all the ions of the group for which experimental data are available, while for the neutral atoms it is more variable, but of the same general magnitude. A calculation of the magnitude of the effect is attempted from first principles, starting from the Hartree–Fock self-consistent wave functions as a first approximation, and adding configurations in which 3 s -, 2 s - and 1 s -electrons are promoted. The promotion of a 3 s -electron is described by an integro-differential equation, which has been solved numerically in one particular case. The contribution turns out of the right sign but ten times smaller than the observed value. Promotion of 2 s - and l s -electrons yield similar equations, which, however, have not been solved, owing to the excessive labour involved. There is no reason to believe that they would not give smaller contributions still. The full explanation of the s -electron effect is thus still an open question.

Study of charge transfer in FeTi

1983 ◽  
Vol 41 ◽  
pp. 296-297
Author(s):  
J. Taft∅
Keyword(s):  
Charge Transfer ◽  
Charge Distribution ◽  
Electron Scattering ◽  
Periodic System ◽  
Electron Distribution ◽  
Scattering Amplitude ◽  
Transition Elements ◽  
Hartree Fock ◽  
Cscl Structure ◽  
The Right

It is well known that for reflections corresponding to large interplanar spacings (i.e., sin θ/λ small), the electron scattering amplitude, f, is sensitive to the ionicity and to the charge distribution around the atoms. We have used this in order to obtain information about the charge distribution in FeTi, which is a candidate for storage of hydrogen. Our goal is to study the changes in electron distribution in the presence of hydrogen, and also the ionicity of hydrogen in metals, but so far our study has been limited to pure FeTi. FeTi has the CsCl structure and thus Fe and Ti scatter with a phase difference of π into the 100-ref lections. Because Fe (Z = 26) is higher in the periodic system than Ti (Z = 22), an immediate “guess” would be that Fe has a larger scattering amplitude than Ti. However, relativistic Hartree-Fock calculations show that the opposite is the case for the 100-reflection. An explanation for this may be sought in the stronger localization of the d-electrons of the first row transition elements when moving to the right in the periodic table. The tabulated difference between fTi (100) and ffe (100) is small, however, and based on the values of the scattering amplitude for isolated atoms, the kinematical intensity of the 100-reflection is only 5.10-4 of the intensity of the 200-reflection.

Slater–Condon parameters for the transition elements, evaluated from analytical Hartree–Fock functions

1968 ◽  
Vol 46 (19) ◽  
pp. 2228-2229
Author(s):  
Carolyn Fisk ◽  
Serafin Fraga
Keyword(s):  
Negative Ions ◽  
Neutral Atoms ◽  
Transition Elements ◽  
Hartree Fock ◽  
Positive Ions

The Slater–Condon integrals for the positive ions, neutral atoms, and negative ions from Sc to Zn have been evaluated from analytical Hartree–Fock functions.

Individual Differences in Face Identity Processing with Fast Periodic Visual Stimulation

2017 ◽  
Vol 29 (8) ◽  
pp. 1368-1377 ◽  
Author(s):  
Buyun Xu ◽  
Joan Liu-Shuang ◽  
Bruno Rossion ◽  
James Tanaka
Keyword(s):  
Individual Differences ◽  
Visual Stimulation ◽  
High Reliability ◽  
Face Identity ◽  
Growing Body ◽  
Occipitotemporal Cortex ◽  
The Right ◽  
Open Question ◽  
Identity Processing ◽  
Identity Task

A growing body of literature suggests that human individuals differ in their ability to process face identity. These findings mainly stem from explicit behavioral tasks, such as the Cambridge Face Memory Test (CFMT). However, it remains an open question whether such individual differences can be found in the absence of an explicit face identity task and when faces have to be individualized at a single glance. In the current study, we tested 49 participants with a recently developed fast periodic visual stimulation (FPVS) paradigm [Liu-Shuang, J., Norcia, A. M., & Rossion, B. An objective index of individual face discrimination in the right occipitotemporal cortex by means of fast periodic oddball stimulation. Neuropsychologia, 52, 57–72, 2014] in EEG to rapidly, objectively, and implicitly quantify face identity processing. In the FPVS paradigm, one face identity (A) was presented at the frequency of 6 Hz, allowing only one gaze fixation, with different face identities (B, C, D) presented every fifth face (1.2 Hz; i.e., AAAABAAAACAAAAD…). Results showed a face individuation response at 1.2 Hz and its harmonics, peaking over occipitotemporal locations. The magnitude of this response showed high reliability across different recording sequences and was significant in all but two participants, with the magnitude and lateralization differing widely across participants. There was a modest but significant correlation between the individuation response amplitude and the performance of the behavioral CFMT task, despite the fact that CFMT and FPVS measured different aspects of face identity processing. Taken together, the current study highlights the FPVS approach as a promising means for studying individual differences in face identity processing.

Introduction

2021 ◽  
pp. 1-13
Author(s):  
Johannes Socher
Keyword(s):  
International Law ◽  
Academic Discipline ◽  
Self Determination ◽  
Raw Material ◽  
Legal Argumentation ◽  
Power Politics ◽  
State Practice ◽  
Detailed Assessment ◽  
The Right ◽  
Open Question

The book provides a detailed assessment of Russia’s state practice in the post-Soviet space with the aim to ascertain a distinct Russian approach to the right of peoples to self-determination, illustrated by seven case studies on the secessionist conflicts over Abkhazia, Chechnya, Crimea, Nagorno-Karabakh, South Ossetia, Tatarstan, and Transnistria. As such, it may serve as a detailed documentation of the raw material necessary to form and identify rules of customary international law, produced by one particular state. Beyond that, it seeks to test the accuracy of and give substance to Lauri Mälksoo’s general assessment in Russian Approaches to International Law that the ‘evolution of Moscow’s legal argumentation and views in these complex cases … has not followed some overarching legal principle but reflected changing power politics. Until 2014, Russia claimed that sovereignty trumped self-determination but in 2014 partly destroyed its own earlier argumentation by its own actions in Ukraine.’ Finally, this book is a contribution to what Mälksoo calls the ‘debatable nexus’ between legal scholarship and state practice of international law in Russia, that is the open question of to what extent international law as an academic discipline continues to be subjugated to the raison d’état in Russia.

Analytical Hartree‐Fock wavefunctions for the neutral atoms from helium to xenon

1974 ◽  
Vol 60 (8) ◽  
pp. 3342-3342 ◽  
Author(s):  
Carla Roetti ◽  
Enrico Clementi
Keyword(s):  
Neutral Atoms ◽  
Hartree Fock

scholarly journals Dyson line and modified Dyson line in the EPR measurements

Nukleonika ◽  
2015 ◽  
Vol 60 (3) ◽  
pp. 385-388 ◽  
Author(s):  
Volodymyr Popovych ◽  
Mariusz Bester ◽  
Ireneusz Stefaniuk ◽  
Marian Kuzma
Keyword(s):  
Electron Paramagnetic Resonance ◽  
Line Shape ◽  
Resonance Line ◽  
Shape Parameter ◽  
Resonance Field ◽  
Ferromagnetic Semiconductors ◽  
Paramagnetic Resonance ◽  
The Right ◽  
Electron Paramagnetic ◽  
Line Shape Parameter

Abstract The difficulty in determining the electron paramagnetic resonance (EPR) line parameters of ferromagnetic semiconductors has been addressed. For these materials, the resonance line is very broad and lies at low resonance field, so that only a part of the line can be detected experimentally. Moreover, the line is of asymmetric (Dysonian) shape as described by the line shape parameter α. We have compared values of line parameters derived by computer fitting of the whole experimental EPR line to the Dyson function (or modified Dyson function) with the values obtained by applying this procedure to the left and the right half of the line.

ELECTRONIC PROPERTIES OF STABLE QUASICRYSTALS CONTAINING TRANSITION ELEMENTS

1993 ◽  
Vol 07 (01n03) ◽  
pp. 318-321
Author(s):  
D. MAYOU ◽  
G. TRAMBLY DE LAISSARDIERE ◽  
F. CYROT-LACKMANN
Keyword(s):  
Bound State ◽  
Partial Density ◽  
Transition Elements ◽  
Hartree Fock ◽  
Anderson Hamiltonian ◽  
Metal Atoms ◽  
Transition Metal Atoms ◽  
First Results ◽  
D Orbitals ◽  
Good Agreement

A model describing the electronic structure of transition metal atoms in Hume-Rothery alloys and quasicrystals is constructed. We start from the classical Anderson hamiltonian, and add a potential [Formula: see text] that describes the diffraction of conduction electrons by Bragg planes near the Fermi surface. Strong deviation from the virtual bound state is observed for realistic parameters. Furthermore the scattering of the conduction states by the d-orbitals changes the partial density of conduction states. This results in a contribution to the apparent negative valency of transition elements in Hume-Rothery alloys. The results are systematically compared with ab-initio calculations for a series of Hume-Rothery alloys and are in good agreement. The magnetic properties are discussed and it is shown that in a simple Hartree-Fock scheme the Stoner Criterion does not apply to these systems due to the peculiar sp-d hybridization effects. First results taking correlations into account are also discussed.

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