https://dictionary.iucr.org/index.php?title=Absorption_threshold&feed=atom&action=historyAbsorption threshold - Revision history2024-03-28T16:56:34ZRevision history for this page on the wikiMediaWiki 1.30.0https://dictionary.iucr.org/index.php?title=Absorption_threshold&diff=4366&oldid=prevBrianMcMahon: Tidied translations and added German and Spanish (U. Mueller)2017-11-08T17:41:26Z<p>Tidied translations and added German and Spanish (U. Mueller)</p>
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<tr><td class='diff-marker'>−</td><td style="color:black; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #ffe49c; vertical-align: top; white-space: pre-wrap;"><div><<del class="diffchange diffchange-inline">Font </del>color="blue">Seuil d'absorption</font> (''Fr''). <<del class="diffchange diffchange-inline">Font </del>color="<del class="diffchange diffchange-inline">it</del>">Soglia d'assorbimento</font> (''It''). <<del class="diffchange diffchange-inline">Font </del>color="purple">吸収限界値</font> (''Ja'').</div></td><td class='diff-marker'>+</td><td style="color:black; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div><<ins class="diffchange diffchange-inline">font </ins>color="blue">Seuil d'absorption</font> (''Fr''). <<ins class="diffchange diffchange-inline">font color="red">Absorptionsschwelle</font> (''Ge''). <font </ins>color="<ins class="diffchange diffchange-inline">black</ins>">Soglia d'assorbimento</font> (''It''). <<ins class="diffchange diffchange-inline">font </ins>color="purple">吸収限界値</font> (''Ja<ins class="diffchange diffchange-inline">''). <font color="green">Umbral de absorción</font> (''Sp</ins>'').  </div></td></tr>
<tr><td class='diff-marker'> </td><td style="background-color: #f9f9f9; color: #333333; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #e6e6e6; vertical-align: top; white-space: pre-wrap;"></td><td class='diff-marker'> </td><td style="background-color: #f9f9f9; color: #333333; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #e6e6e6; vertical-align: top; white-space: pre-wrap;"></td></tr>
<tr><td class='diff-marker'> </td><td style="background-color: #f9f9f9; color: #333333; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #e6e6e6; vertical-align: top; white-space: pre-wrap;"><div>== Definition ==</div></td><td class='diff-marker'> </td><td style="background-color: #f9f9f9; color: #333333; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #e6e6e6; vertical-align: top; white-space: pre-wrap;"><div>== Definition ==</div></td></tr>
</table>BrianMcMahonhttps://dictionary.iucr.org/index.php?title=Absorption_threshold&diff=4174&oldid=prevBrianMcMahon: Style edits to align with printed edition2017-05-19T10:15:46Z<p>Style edits to align with printed edition</p>
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<tr><td class='diff-marker'> </td><td style="background-color: #f9f9f9; color: #333333; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #e6e6e6; vertical-align: top; white-space: pre-wrap;"><div>(3) Experimentally, the absorption threshold is sometimes defined as the inflection point in the first derivative of the experimental edge spectrum (the point of maximum slope on the rising edge for a particular sub-shell); this is a convenient marker for experimentalists but (''a'') it is source (beamline) and bandwidth dependent; (''b'') it is affected by pre-edge structure and the Fermi level (cross link) due to potential contributions from bound-bound channels; (''c'') the experimental edge may contain two or more such inflection points, and the determination depends upon instrumental resolution.</div></td><td class='diff-marker'> </td><td style="background-color: #f9f9f9; color: #333333; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #e6e6e6; vertical-align: top; white-space: pre-wrap;"><div>(3) Experimentally, the absorption threshold is sometimes defined as the inflection point in the first derivative of the experimental edge spectrum (the point of maximum slope on the rising edge for a particular sub-shell); this is a convenient marker for experimentalists but (''a'') it is source (beamline) and bandwidth dependent; (''b'') it is affected by pre-edge structure and the Fermi level (cross link) due to potential contributions from bound-bound channels; (''c'') the experimental edge may contain two or more such inflection points, and the determination depends upon instrumental resolution.</div></td></tr>
<tr><td class='diff-marker'> </td><td style="background-color: #f9f9f9; color: #333333; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #e6e6e6; vertical-align: top; white-space: pre-wrap;"></td><td class='diff-marker'> </td><td style="background-color: #f9f9f9; color: #333333; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #e6e6e6; vertical-align: top; white-space: pre-wrap;"></td></tr>
<tr><td class='diff-marker'>−</td><td style="color:black; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #ffe49c; vertical-align: top; white-space: pre-wrap;"><div>(4) Experimentally, the absorption threshold is sometimes defined as the point exactly 50% of the jump ratio from the background absorption (from other shells, including scattering) to the peak absorption coefficient of the XANES spectrum, defined either by the clear maximum or by the smooth line representing the background to be subtracted in the determination of <math>\chi(k)</math> (<del class="diffchange diffchange-inline">''</del>see<del class="diffchange diffchange-inline">'' </del>[[X-ray absorption fine structure (XAFS)<del class="diffchange diffchange-inline">|XAFS</del>]]); this is a problematic measure, since it depends upon beam-line dependent effects [(3) above], and a wide variety of different predictions of the 'true background level’ <math>\mu_0</math> above the edge (<del class="diffchange diffchange-inline">''</del>see<del class="diffchange diffchange-inline">'' </del>[[X-ray absorption fine structure (XAFS)|XAFS]]).  </div></td><td class='diff-marker'>+</td><td style="color:black; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div>(4) Experimentally, the absorption threshold is sometimes defined as the point exactly 50% of the jump ratio from the background absorption (from other shells, including scattering) to the peak absorption coefficient of the XANES spectrum, defined either by the clear maximum or by the smooth line representing the background to be subtracted in the determination of <math>\chi(k)</math> (see [[X-ray absorption fine structure (XAFS)]]); this is a problematic measure, since it depends upon beam-line dependent effects [(3) above], and a wide variety of different predictions of the 'true background level’ <math>\mu_0</math> above the edge (see [[X-ray absorption fine structure (XAFS)|XAFS]]).  </div></td></tr>
<tr><td class='diff-marker'> </td><td style="background-color: #f9f9f9; color: #333333; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #e6e6e6; vertical-align: top; white-space: pre-wrap;"></td><td class='diff-marker'> </td><td style="background-color: #f9f9f9; color: #333333; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #e6e6e6; vertical-align: top; white-space: pre-wrap;"></td></tr>
<tr><td class='diff-marker'> </td><td style="background-color: #f9f9f9; color: #333333; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #e6e6e6; vertical-align: top; white-space: pre-wrap;"><div>(5) Computationally, an absorption threshold is defined for XAFS fitting (and occasionally XANES fitting) as <math>E_0</math> which is considered either as an arbitrary fitting coefficient or the starting point of the <math>k</math> transform, which in turn generates the Fourier transform for the XAFS structure <math>\chi(k)</math>; as the latter, it should be defined as per (1) above; as the former, this will often yield a function of <math>r</math> and errors in <math>E_0</math> of order 10 eV or more which can result in bond length errors of order 0.02 Å or more.</div></td><td class='diff-marker'> </td><td style="background-color: #f9f9f9; color: #333333; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #e6e6e6; vertical-align: top; white-space: pre-wrap;"><div>(5) Computationally, an absorption threshold is defined for XAFS fitting (and occasionally XANES fitting) as <math>E_0</math> which is considered either as an arbitrary fitting coefficient or the starting point of the <math>k</math> transform, which in turn generates the Fourier transform for the XAFS structure <math>\chi(k)</math>; as the latter, it should be defined as per (1) above; as the former, this will often yield a function of <math>r</math> and errors in <math>E_0</math> of order 10 eV or more which can result in bond length errors of order 0.02 Å or more.</div></td></tr>
</table>BrianMcMahonhttps://dictionary.iucr.org/index.php?title=Absorption_threshold&diff=4173&oldid=prevBrianMcMahon at 09:54, 19 May 20172017-05-19T09:54:32Z<p></p>
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<td colspan="2" style="background-color: white; color:black; text-align: center;">Revision as of 09:54, 19 May 2017</td>
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<tr><td class='diff-marker'>−</td><td style="color:black; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #ffe49c; vertical-align: top; white-space: pre-wrap;"><div><Font color="blue">Seuil d'absorption</font> (''Fr'')<del class="diffchange diffchange-inline">; </del><Font color="it">Soglia d'assorbimento</font> (''It'')<del class="diffchange diffchange-inline">; </del><Font color="purple">吸収限界値</font> (''Ja'').</div></td><td class='diff-marker'>+</td><td style="color:black; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div><Font color="blue">Seuil d'absorption</font> (''Fr'')<ins class="diffchange diffchange-inline">. </ins><Font color="it">Soglia d'assorbimento</font> (''It'')<ins class="diffchange diffchange-inline">. </ins><Font color="purple">吸収限界値</font> (''Ja'').</div></td></tr>
<tr><td class='diff-marker'> </td><td style="background-color: #f9f9f9; color: #333333; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #e6e6e6; vertical-align: top; white-space: pre-wrap;"></td><td class='diff-marker'> </td><td style="background-color: #f9f9f9; color: #333333; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #e6e6e6; vertical-align: top; white-space: pre-wrap;"></td></tr>
<tr><td class='diff-marker'> </td><td style="background-color: #f9f9f9; color: #333333; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #e6e6e6; vertical-align: top; white-space: pre-wrap;"><div>== Definition ==</div></td><td class='diff-marker'> </td><td style="background-color: #f9f9f9; color: #333333; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #e6e6e6; vertical-align: top; white-space: pre-wrap;"><div>== Definition ==</div></td></tr>
<tr><td class='diff-marker'> </td><td style="background-color: #f9f9f9; color: #333333; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #e6e6e6; vertical-align: top; white-space: pre-wrap;"></td><td class='diff-marker'> </td><td style="background-color: #f9f9f9; color: #333333; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #e6e6e6; vertical-align: top; white-space: pre-wrap;"></td></tr>
<tr><td class='diff-marker'>−</td><td style="color:black; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #ffe49c; vertical-align: top; white-space: pre-wrap;"><div>In the literature there is much confusion, even in modern papers, concerning the definition of the absorption threshold. The absorption threshold should indicate the first allowed transition in an absorption spectrum. Many definitions are used in common parlance. In practice, they yield very different values in common analysis. We present and comment upon the most commonly used:</div></td><td class='diff-marker'>+</td><td style="color:black; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div>In the literature there is much confusion, even in modern papers, concerning the definition of the <ins class="diffchange diffchange-inline">'''</ins>absorption threshold<ins class="diffchange diffchange-inline">'''</ins>. The absorption threshold should indicate the first allowed transition in an absorption spectrum. Many definitions are used in common parlance. In practice, they yield very different values in common analysis. We present and comment upon the most commonly used:</div></td></tr>
<tr><td class='diff-marker'> </td><td style="background-color: #f9f9f9; color: #333333; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #e6e6e6; vertical-align: top; white-space: pre-wrap;"></td><td class='diff-marker'> </td><td style="background-color: #f9f9f9; color: #333333; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #e6e6e6; vertical-align: top; white-space: pre-wrap;"></td></tr>
<tr><td class='diff-marker'>−</td><td style="color:black; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #ffe49c; vertical-align: top; white-space: pre-wrap;"><div>(1) The energy at which the open continuum channel for photo-electric absorption becomes available, producing a continuum photo-electron. This has an exact value from theory, subject to convergence issues (<del class="diffchange diffchange-inline">''</del>see<del class="diffchange diffchange-inline">'' </del>[[Fermi energy]]).</div></td><td class='diff-marker'>+</td><td style="color:black; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div>(1) The energy at which the open continuum channel for photo-electric absorption becomes available, producing a continuum photo-electron. This has an exact value from theory, subject to convergence issues (see [[Fermi energy]]).</div></td></tr>
<tr><td class='diff-marker'> </td><td style="background-color: #f9f9f9; color: #333333; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #e6e6e6; vertical-align: top; white-space: pre-wrap;"></td><td class='diff-marker'> </td><td style="background-color: #f9f9f9; color: #333333; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #e6e6e6; vertical-align: top; white-space: pre-wrap;"></td></tr>
<tr><td class='diff-marker'>−</td><td style="color:black; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #ffe49c; vertical-align: top; white-space: pre-wrap;"><div>(2) A (higher) energy at which a secondary (two-step) photoionization channel becomes energetically possible (<del class="diffchange diffchange-inline">see </del>shake-up, shake-off); in general this is more challenging to compute theoretically, and is less easily separable in conventional XAS experimental data, but can be investigated incisively in RIXS, XFS and related spectroscopies.</div></td><td class='diff-marker'>+</td><td style="color:black; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div>(2) A (higher) energy at which a secondary (two-step) photoionization channel becomes energetically possible (<ins class="diffchange diffchange-inline">'</ins>shake-up<ins class="diffchange diffchange-inline">'</ins>, <ins class="diffchange diffchange-inline">'</ins>shake-off<ins class="diffchange diffchange-inline">'; see [[multi-electron excitations]]</ins>); in general this is more challenging to compute theoretically, and is less easily separable in conventional XAS experimental data, but can be investigated incisively in RIXS, XFS and related spectroscopies.</div></td></tr>
<tr><td class='diff-marker'> </td><td style="background-color: #f9f9f9; color: #333333; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #e6e6e6; vertical-align: top; white-space: pre-wrap;"></td><td class='diff-marker'> </td><td style="background-color: #f9f9f9; color: #333333; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #e6e6e6; vertical-align: top; white-space: pre-wrap;"></td></tr>
<tr><td class='diff-marker'>−</td><td style="color:black; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #ffe49c; vertical-align: top; white-space: pre-wrap;"><div>(3) Experimentally, the absorption threshold is sometimes defined as the inflection point in the first derivative of the experimental edge spectrum (the point of maximum slope on the rising edge for a particular sub-shell); this is a convenient marker for experimentalists but <del class="diffchange diffchange-inline">&ndash; </del>(''a'') it is source (<del class="diffchange diffchange-inline">beam-line</del>) and <del class="diffchange diffchange-inline">band-width </del>dependent; (''b'') it is affected by pre-edge structure and the Fermi level (cross link) due to potential contributions from bound-bound channels; (''c'') the experimental edge may contain two or more such inflection points, and the determination depends upon instrumental resolution.</div></td><td class='diff-marker'>+</td><td style="color:black; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div>(3) Experimentally, the absorption threshold is sometimes defined as the inflection point in the first derivative of the experimental edge spectrum (the point of maximum slope on the rising edge for a particular sub-shell); this is a convenient marker for experimentalists but (''a'') it is source (<ins class="diffchange diffchange-inline">beamline</ins>) and <ins class="diffchange diffchange-inline">bandwidth </ins>dependent; (''b'') it is affected by pre-edge structure and the Fermi level (cross link) due to potential contributions from bound-bound channels; (''c'') the experimental edge may contain two or more such inflection points, and the determination depends upon instrumental resolution.</div></td></tr>
<tr><td class='diff-marker'> </td><td style="background-color: #f9f9f9; color: #333333; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #e6e6e6; vertical-align: top; white-space: pre-wrap;"></td><td class='diff-marker'> </td><td style="background-color: #f9f9f9; color: #333333; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #e6e6e6; vertical-align: top; white-space: pre-wrap;"></td></tr>
<tr><td class='diff-marker'> </td><td style="background-color: #f9f9f9; color: #333333; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #e6e6e6; vertical-align: top; white-space: pre-wrap;"><div>(4) Experimentally, the absorption threshold is sometimes defined as the point exactly 50% of the jump ratio from the background absorption (from other shells, including scattering) to the peak absorption coefficient of the XANES spectrum, defined either by the clear maximum or by the smooth line representing the background to be subtracted in the determination of <math>\chi(k)</math> (''see'' [[X-ray absorption fine structure (XAFS)|XAFS]]); this is a problematic measure, since it depends upon beam-line dependent effects [(3) above], and a wide variety of different predictions of the 'true background level’ <math>\mu_0</math> above the edge (''see'' [[X-ray absorption fine structure (XAFS)|XAFS]]).  </div></td><td class='diff-marker'> </td><td style="background-color: #f9f9f9; color: #333333; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #e6e6e6; vertical-align: top; white-space: pre-wrap;"><div>(4) Experimentally, the absorption threshold is sometimes defined as the point exactly 50% of the jump ratio from the background absorption (from other shells, including scattering) to the peak absorption coefficient of the XANES spectrum, defined either by the clear maximum or by the smooth line representing the background to be subtracted in the determination of <math>\chi(k)</math> (''see'' [[X-ray absorption fine structure (XAFS)|XAFS]]); this is a problematic measure, since it depends upon beam-line dependent effects [(3) above], and a wide variety of different predictions of the 'true background level’ <math>\mu_0</math> above the edge (''see'' [[X-ray absorption fine structure (XAFS)|XAFS]]).  </div></td></tr>
</table>BrianMcMahonhttps://dictionary.iucr.org/index.php?title=Absorption_threshold&diff=3765&oldid=prevMassimoNespolo: Ja2016-10-04T11:12:55Z<p>Ja</p>
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<td colspan="2" style="background-color: white; color:black; text-align: center;">Revision as of 11:12, 4 October 2016</td>
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<tr><td class='diff-marker'>−</td><td style="color:black; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #ffe49c; vertical-align: top; white-space: pre-wrap;"><div><Font color="blue">Seuil d'absorption</font> (''Fr''); <Font color="it">Soglia d'assorbimento</font> (''It'').</div></td><td class='diff-marker'>+</td><td style="color:black; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div><Font color="blue">Seuil d'absorption</font> (''Fr''); <Font color="it">Soglia d'assorbimento</font> (''It<ins class="diffchange diffchange-inline">''); <Font color="purple">吸収限界値</font> (''Ja</ins>'').</div></td></tr>
<tr><td class='diff-marker'> </td><td style="background-color: #f9f9f9; color: #333333; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #e6e6e6; vertical-align: top; white-space: pre-wrap;"></td><td class='diff-marker'> </td><td style="background-color: #f9f9f9; color: #333333; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #e6e6e6; vertical-align: top; white-space: pre-wrap;"></td></tr>
<tr><td class='diff-marker'> </td><td style="background-color: #f9f9f9; color: #333333; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #e6e6e6; vertical-align: top; white-space: pre-wrap;"><div>== Definition ==</div></td><td class='diff-marker'> </td><td style="background-color: #f9f9f9; color: #333333; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #e6e6e6; vertical-align: top; white-space: pre-wrap;"><div>== Definition ==</div></td></tr>
</table>MassimoNespolohttps://dictionary.iucr.org/index.php?title=Absorption_threshold&diff=3698&oldid=prevMassimoNespolo: languages, ol in the see also section2016-04-13T15:00:48Z<p>languages, ol in the see also section</p>
<table class="diff diff-contentalign-left" data-mw="interface">
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<td colspan="2" style="background-color: white; color:black; text-align: center;">← Older revision</td>
<td colspan="2" style="background-color: white; color:black; text-align: center;">Revision as of 15:00, 13 April 2016</td>
</tr><tr><td colspan="2" class="diff-lineno" id="mw-diff-left-l1" >Line 1:</td>
<td colspan="2" class="diff-lineno">Line 1:</td></tr>
<tr><td colspan="2"> </td><td class='diff-marker'>+</td><td style="color:black; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div><ins style="font-weight: bold; text-decoration: none;"><Font color="blue">Seuil d'absorption</font> (''Fr''); <Font color="it">Soglia d'assorbimento</font> (''It'').</ins></div></td></tr>
<tr><td colspan="2"> </td><td class='diff-marker'>+</td><td style="color:black; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div><ins style="font-weight: bold; text-decoration: none;"></ins></div></td></tr>
<tr><td class='diff-marker'> </td><td style="background-color: #f9f9f9; color: #333333; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #e6e6e6; vertical-align: top; white-space: pre-wrap;"><div>== Definition ==</div></td><td class='diff-marker'> </td><td style="background-color: #f9f9f9; color: #333333; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #e6e6e6; vertical-align: top; white-space: pre-wrap;"><div>== Definition ==</div></td></tr>
<tr><td class='diff-marker'> </td><td style="background-color: #f9f9f9; color: #333333; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #e6e6e6; vertical-align: top; white-space: pre-wrap;"></td><td class='diff-marker'> </td><td style="background-color: #f9f9f9; color: #333333; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #e6e6e6; vertical-align: top; white-space: pre-wrap;"></td></tr>
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<tr><td class='diff-marker'> </td><td style="background-color: #f9f9f9; color: #333333; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #e6e6e6; vertical-align: top; white-space: pre-wrap;"></td><td class='diff-marker'> </td><td style="background-color: #f9f9f9; color: #333333; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #e6e6e6; vertical-align: top; white-space: pre-wrap;"></td></tr>
<tr><td class='diff-marker'> </td><td style="background-color: #f9f9f9; color: #333333; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #e6e6e6; vertical-align: top; white-space: pre-wrap;"><div>== See also ==</div></td><td class='diff-marker'> </td><td style="background-color: #f9f9f9; color: #333333; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #e6e6e6; vertical-align: top; white-space: pre-wrap;"><div>== See also ==</div></td></tr>
<tr><td class='diff-marker'>−</td><td style="color:black; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #ffe49c; vertical-align: top; white-space: pre-wrap;"><div>[[Fermi level]]<del class="diffchange diffchange-inline">/</del>[[Fermi energy]]</div></td><td class='diff-marker'>+</td><td style="color:black; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div><ins class="diffchange diffchange-inline">*</ins>[[Fermi level]]</div></td></tr>
<tr><td colspan="2"> </td><td class='diff-marker'>+</td><td style="color:black; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div><ins class="diffchange diffchange-inline">*</ins>[[Fermi energy]]</div></td></tr>
<tr><td class='diff-marker'> </td><td style="background-color: #f9f9f9; color: #333333; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #e6e6e6; vertical-align: top; white-space: pre-wrap;"></td><td class='diff-marker'> </td><td style="background-color: #f9f9f9; color: #333333; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #e6e6e6; vertical-align: top; white-space: pre-wrap;"></td></tr>
<tr><td class='diff-marker'> </td><td style="background-color: #f9f9f9; color: #333333; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #e6e6e6; vertical-align: top; white-space: pre-wrap;"><div>[[Category:X-ray absorption spectroscopy]]</div></td><td class='diff-marker'> </td><td style="background-color: #f9f9f9; color: #333333; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #e6e6e6; vertical-align: top; white-space: pre-wrap;"><div>[[Category:X-ray absorption spectroscopy]]</div></td></tr>
</table>MassimoNespolohttps://dictionary.iucr.org/index.php?title=Absorption_threshold&diff=3696&oldid=prevBrianMcMahon at 14:37, 13 April 20162016-04-13T14:37:00Z<p></p>
<table class="diff diff-contentalign-left" data-mw="interface">
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<col class="diff-content" />
<col class="diff-marker" />
<col class="diff-content" />
<tr style="vertical-align: top;" lang="en">
<td colspan="2" style="background-color: white; color:black; text-align: center;">← Older revision</td>
<td colspan="2" style="background-color: white; color:black; text-align: center;">Revision as of 14:37, 13 April 2016</td>
</tr><tr><td colspan="2" class="diff-lineno" id="mw-diff-left-l7" >Line 7:</td>
<td colspan="2" class="diff-lineno">Line 7:</td></tr>
<tr><td class='diff-marker'> </td><td style="background-color: #f9f9f9; color: #333333; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #e6e6e6; vertical-align: top; white-space: pre-wrap;"><div>(2) A (higher) energy at which a secondary (two-step) photoionization channel becomes energetically possible (see shake-up, shake-off); in general this is more challenging to compute theoretically, and is less easily separable in conventional XAS experimental data, but can be investigated incisively in RIXS, XFS and related spectroscopies.</div></td><td class='diff-marker'> </td><td style="background-color: #f9f9f9; color: #333333; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #e6e6e6; vertical-align: top; white-space: pre-wrap;"><div>(2) A (higher) energy at which a secondary (two-step) photoionization channel becomes energetically possible (see shake-up, shake-off); in general this is more challenging to compute theoretically, and is less easily separable in conventional XAS experimental data, but can be investigated incisively in RIXS, XFS and related spectroscopies.</div></td></tr>
<tr><td class='diff-marker'> </td><td style="background-color: #f9f9f9; color: #333333; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #e6e6e6; vertical-align: top; white-space: pre-wrap;"></td><td class='diff-marker'> </td><td style="background-color: #f9f9f9; color: #333333; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #e6e6e6; vertical-align: top; white-space: pre-wrap;"></td></tr>
<tr><td class='diff-marker'>−</td><td style="color:black; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #ffe49c; vertical-align: top; white-space: pre-wrap;"><div>(3) Experimentally, the absorption threshold is sometimes defined as the inflection point in the first derivative of the experimental edge spectrum (the point of maximum slope on the rising edge for a particular sub-shell); this is a convenient marker for experimentalists but &ndash<del class="diffchange diffchange-inline">' </del>(''a'') it is source (beam-line) and band-width dependent; (''b'') it is affected by pre-edge structure and the Fermi level (cross link) due to potential contributions from bound-bound channels; (''c'') the experimental edge may contain two or more such inflection points, and the determination depends upon instrumental resolution.</div></td><td class='diff-marker'>+</td><td style="color:black; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div>(3) Experimentally, the absorption threshold is sometimes defined as the inflection point in the first derivative of the experimental edge spectrum (the point of maximum slope on the rising edge for a particular sub-shell); this is a convenient marker for experimentalists but &ndash<ins class="diffchange diffchange-inline">; </ins>(''a'') it is source (beam-line) and band-width dependent; (''b'') it is affected by pre-edge structure and the Fermi level (cross link) due to potential contributions from bound-bound channels; (''c'') the experimental edge may contain two or more such inflection points, and the determination depends upon instrumental resolution.</div></td></tr>
<tr><td class='diff-marker'> </td><td style="background-color: #f9f9f9; color: #333333; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #e6e6e6; vertical-align: top; white-space: pre-wrap;"></td><td class='diff-marker'> </td><td style="background-color: #f9f9f9; color: #333333; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #e6e6e6; vertical-align: top; white-space: pre-wrap;"></td></tr>
<tr><td class='diff-marker'>−</td><td style="color:black; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #ffe49c; vertical-align: top; white-space: pre-wrap;"><div>(4) Experimentally, the absorption threshold is sometimes defined as the point exactly 50% of the jump ratio from the background absorption (from other shells, including scattering) to the peak absorption coefficient of the XANES spectrum, defined either by the clear maximum or by the smooth line representing the background to be subtracted in the determination of <math>\chi(k)</math> (''see'' [[X-ray absorption fine structure (XAFS)|XAFS]]); this is a problematic measure, since it depends upon beam-line dependent effects [(3) above], and a wide variety of different predictions of the 'true background level’ <math>\mu_0</math> above the edge <del class="diffchange diffchange-inline">(</del>(''see'' [[X-ray absorption fine structure (XAFS)|XAFS]]).  </div></td><td class='diff-marker'>+</td><td style="color:black; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div>(4) Experimentally, the absorption threshold is sometimes defined as the point exactly 50% of the jump ratio from the background absorption (from other shells, including scattering) to the peak absorption coefficient of the XANES spectrum, defined either by the clear maximum or by the smooth line representing the background to be subtracted in the determination of <math>\chi(k)</math> (''see'' [[X-ray absorption fine structure (XAFS)|XAFS]]); this is a problematic measure, since it depends upon beam-line dependent effects [(3) above], and a wide variety of different predictions of the 'true background level’ <math>\mu_0</math> above the edge (''see'' [[X-ray absorption fine structure (XAFS)|XAFS]]).  </div></td></tr>
<tr><td class='diff-marker'> </td><td style="background-color: #f9f9f9; color: #333333; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #e6e6e6; vertical-align: top; white-space: pre-wrap;"></td><td class='diff-marker'> </td><td style="background-color: #f9f9f9; color: #333333; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #e6e6e6; vertical-align: top; white-space: pre-wrap;"></td></tr>
<tr><td class='diff-marker'> </td><td style="background-color: #f9f9f9; color: #333333; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #e6e6e6; vertical-align: top; white-space: pre-wrap;"><div>(5) Computationally, an absorption threshold is defined for XAFS fitting (and occasionally XANES fitting) as <math>E_0</math> which is considered either as an arbitrary fitting coefficient or the starting point of the <math>k</math> transform, which in turn generates the Fourier transform for the XAFS structure <math>\chi(k)</math>; as the latter, it should be defined as per (1) above; as the former, this will often yield a function of <math>r</math> and errors in <math>E_0</math> of order 10 eV or more which can result in bond length errors of order 0.02 Å or more.</div></td><td class='diff-marker'> </td><td style="background-color: #f9f9f9; color: #333333; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #e6e6e6; vertical-align: top; white-space: pre-wrap;"><div>(5) Computationally, an absorption threshold is defined for XAFS fitting (and occasionally XANES fitting) as <math>E_0</math> which is considered either as an arbitrary fitting coefficient or the starting point of the <math>k</math> transform, which in turn generates the Fourier transform for the XAFS structure <math>\chi(k)</math>; as the latter, it should be defined as per (1) above; as the former, this will often yield a function of <math>r</math> and errors in <math>E_0</math> of order 10 eV or more which can result in bond length errors of order 0.02 Å or more.</div></td></tr>
</table>BrianMcMahonhttps://dictionary.iucr.org/index.php?title=Absorption_threshold&diff=3695&oldid=prevBrianMcMahon: Created page with "== Definition == In the literature there is much confusion, even in modern papers, concerning the definition of the absorption threshold. The absorption threshold should indicat..."2016-04-13T14:35:47Z<p>Created page with "== Definition == In the literature there is much confusion, even in modern papers, concerning the definition of the absorption threshold. The absorption threshold should indicat..."</p>
<p><b>New page</b></p><div>== Definition ==<br />
<br />
In the literature there is much confusion, even in modern papers, concerning the definition of the absorption threshold. The absorption threshold should indicate the first allowed transition in an absorption spectrum. Many definitions are used in common parlance. In practice, they yield very different values in common analysis. We present and comment upon the most commonly used:<br />
<br />
(1) The energy at which the open continuum channel for photo-electric absorption becomes available, producing a continuum photo-electron. This has an exact value from theory, subject to convergence issues (''see'' [[Fermi energy]]).<br />
<br />
(2) A (higher) energy at which a secondary (two-step) photoionization channel becomes energetically possible (see shake-up, shake-off); in general this is more challenging to compute theoretically, and is less easily separable in conventional XAS experimental data, but can be investigated incisively in RIXS, XFS and related spectroscopies.<br />
<br />
(3) Experimentally, the absorption threshold is sometimes defined as the inflection point in the first derivative of the experimental edge spectrum (the point of maximum slope on the rising edge for a particular sub-shell); this is a convenient marker for experimentalists but &ndash' (''a'') it is source (beam-line) and band-width dependent; (''b'') it is affected by pre-edge structure and the Fermi level (cross link) due to potential contributions from bound-bound channels; (''c'') the experimental edge may contain two or more such inflection points, and the determination depends upon instrumental resolution.<br />
<br />
(4) Experimentally, the absorption threshold is sometimes defined as the point exactly 50% of the jump ratio from the background absorption (from other shells, including scattering) to the peak absorption coefficient of the XANES spectrum, defined either by the clear maximum or by the smooth line representing the background to be subtracted in the determination of <math>\chi(k)</math> (''see'' [[X-ray absorption fine structure (XAFS)|XAFS]]); this is a problematic measure, since it depends upon beam-line dependent effects [(3) above], and a wide variety of different predictions of the 'true background level’ <math>\mu_0</math> above the edge ((''see'' [[X-ray absorption fine structure (XAFS)|XAFS]]). <br />
<br />
(5) Computationally, an absorption threshold is defined for XAFS fitting (and occasionally XANES fitting) as <math>E_0</math> which is considered either as an arbitrary fitting coefficient or the starting point of the <math>k</math> transform, which in turn generates the Fourier transform for the XAFS structure <math>\chi(k)</math>; as the latter, it should be defined as per (1) above; as the former, this will often yield a function of <math>r</math> and errors in <math>E_0</math> of order 10 eV or more which can result in bond length errors of order 0.02 Å or more.<br />
<br />
Both computationally and experimentally, the energy axis is often not defined except in a relative sense, so that inconsistencies between the implementations of these definitions are at this point relatively common.<br />
<br />
== See also ==<br />
[[Fermi level]]/[[Fermi energy]]<br />
<br />
[[Category:X-ray absorption spectroscopy]]</div>BrianMcMahon