X-ray absorption fine structure (XAFS) - Revision history

MassimoNespolo: Lang

2018-12-19T02:43:07Z

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BrianMcMahon: Style edits to align with printed edition

2017-05-20T11:46:38Z

Style edits to align with printed edition

BrianMcMahon at 15:38, 13 April 2016

2016-04-13T15:38:50Z

BrianMcMahon at 14:23, 13 April 2016

2016-04-13T14:23:34Z

BrianMcMahon: Created page with "== Definition == '''X-ray absorption fine structure''' (XAFS) is the modulation of the absorption coefficient (''q.v.'') at and above an absorption edge (''q.v.'') of an ..."

2016-04-13T14:10:02Z

Created page with "== Definition == '''X-ray absorption fine structure''' (XAFS) is the modulation of the absorption coefficient (''q.v.'') at and above an absorption edge (''q.v.'') of an ..."

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== Definition ==
'''X-ray absorption fine structure''' (XAFS) is the modulation of the [[absorption coefficient]] (''q.v.'') at and above an [[absorption edge]] (''q.v.'') of an element due to its chemical state and structure of its immediate surroundings. XAFS is commonly divided into the 'near edge’ region (XANES or NEXAFS) which extends to ~50 eV above the absorption edge and the 'extended’ region (EXAFS) that displays oscillations in the absorption coefficient extending from ~50 eV above the absorption edge.

The distinction in usage for XANES (X-ray absorption near edge spectroscopy) and NEXAFS (near-edge X-ray absorption fine structure) is historical. Generally, XANES is used for hard X-ray edges (~1 keV and above), while NEXAFS is used for soft X-ray edges. Spectral features that occur before the rise of the main absorption edge are referred to as 'pre-edge’ features, associated with transitions to bound states.

The [[extended X-ray absorption fine structure (EXAFS)]] (''q.v.'') region contains modulation of the absorption coefficient that can be interpreted in terms of photo-electron scattering.

In relation to the (linear) absorption coefficient, the XAFS is defined as

<math>\chi(E) = {[\mu(E) - \mu_0(E)]\over\mu_0(E)}</math>

where <math>\mu(E)</math> is the linear absorption coefficient measured or calculated and <math>\mu_0(E)</math> a smooth background as calculated in the absence of scattering or fit (''e.g.'' a spline fit) ''etc.''

The XAFS is often practically defined as

<math>\chi(E) = {[\mu(E) - \mu_0(E)]\over\Delta\mu(E)}</math>

where <math>\mu(E)</math> is either measured or calculated and <math>\Delta\mu(E)</math> is either the jump in absorption at the edge or a reference background that simulates the edge and a smooth atomic-like background.

==See also ==
*[[Absorption coefficient]]
*[[Absorption edge]]
*[[Extended X-ray Absorption Fine Structure (EXAFS)]]

[[Category:X-ray absorption spectroscopy]]

← Older revision		Revision as of 02:43, 19 December 2018
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		+	<font color="blue">Structure fine d'absorption des rayons X</font> (''Fr''). <font color="red">Feinstruktur der Röntgenabsorption</font> (''Ge''). <font color="black">Struttura fine d'assorbimento dei raggi X</font> (''It''). <font color="purple">エックス線吸収微細構造</font> (''Ja''). <font color="brown">Тонкая структура спектров поглощения рентгеновских лучей</font> (''Ru''). <font color="green">Estructura fina de absorción de rayos X</font> (''Sp'').
		+
	== Definition ==		== Definition ==
	'''X-ray absorption fine structure''' (XAFS) is the modulation of the [[absorption coefficient]] at and above an [[absorption edge]] of an element due to its chemical state and structure of its immediate surroundings. XAFS is commonly divided into the 'near edge’ region (XANES or NEXAFS) which extends to ~50 eV above the absorption edge and the 'extended’ region (EXAFS) that displays oscillations in the absorption coefficient extending from ~50 eV above the absorption edge.		'''X-ray absorption fine structure''' (XAFS) is the modulation of the [[absorption coefficient]] at and above an [[absorption edge]] of an element due to its chemical state and structure of its immediate surroundings. XAFS is commonly divided into the 'near edge’ region (XANES or NEXAFS) which extends to ~50 eV above the absorption edge and the 'extended’ region (EXAFS) that displays oscillations in the absorption coefficient extending from ~50 eV above the absorption edge.

@@ Line 1: / Line 1: @@
 == Definition ==
-'''X-ray absorption fine structure''' (XAFS) is the modulation of the [[absorption coefficient]] (''q.v.'') at and above an [[absorption edge]] (''q.v.'') of an element due to its chemical state and structure of its immediate surroundings. XAFS is commonly divided into the 'near edge’ region (XANES or NEXAFS) which extends to ~50 eV above the absorption edge and the 'extended’ region (EXAFS) that displays oscillations in the absorption coefficient extending from ~50 eV above the absorption edge.
+'''X-ray absorption fine structure''' (XAFS) is the modulation of the [[absorption coefficient]] at and above an [[absorption edge]] of an element due to its chemical state and structure of its immediate surroundings. XAFS is commonly divided into the 'near edge’ region (XANES or NEXAFS) which extends to ~50 eV above the absorption edge and the 'extended’ region (EXAFS) that displays oscillations in the absorption coefficient extending from ~50 eV above the absorption edge.
 The distinction in usage for '''XANES''' (X-ray absorption near edge spectroscopy) and '''NEXAFS''' (near-edge X-ray absorption fine structure) is historical. Generally, XANES is used for hard X-ray edges (~1 keV and above), while NEXAFS is used for soft X-ray edges. Spectral features that occur before the rise of the main absorption edge are referred to as 'pre-edge’ features, associated with transitions to bound states.
-The [[extended X-ray absorption fine structure (EXAFS)]] (''q.v.'') region contains modulation of the absorption coefficient that can be interpreted in terms of photo-electron scattering.
+The [[extended X-ray absorption fine structure (EXAFS)]] region contains modulation of the absorption coefficient that can be interpreted in terms of photo-electron scattering.
 In relation to the (linear) absorption coefficient, the XAFS is defined as

@@ Line 21: / Line 21: @@
 *[[Absorption coefficient]]
 *[[Absorption edge]]
-*[[Extended X-ray Absorption Fine Structure (EXAFS)]]
+*[[Extended X-ray absorption fine structure (EXAFS)]]
 [[Category:X-ray absorption spectroscopy]]