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| 9 | <title>2.2.1. Broad peak — Sasmodels</title> |
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| 33 | <div class="header"><h1 class="heading"><a href="../index.html"> |
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| 34 | <span>Home</span></a></h1> |
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| 35 | <h2 class="heading"><span>2.2.1. Broad peak</span></h2> |
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| 49 | |
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| 50 | |
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| 51 | <div class="section" id="broad-peak"> |
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| 52 | <span id="id1"></span><h1>2.2.1. Broad peak<a class="headerlink" href="#broad-peak" title="Permalink to this headline">¶</a></h1> |
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| 53 | <p>Broad Lorentzian type peak on top of a power law decay</p> |
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| 54 | <table border="1" class="docutils"> |
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| 55 | <colgroup> |
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| 56 | <col width="19%" /> |
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| 58 | <col width="11%" /> |
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| 59 | <col width="18%" /> |
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| 60 | </colgroup> |
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| 61 | <thead valign="bottom"> |
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| 62 | <tr class="row-odd"><th class="head">Parameter</th> |
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| 63 | <th class="head">Description</th> |
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| 64 | <th class="head">Units</th> |
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| 65 | <th class="head">Default value</th> |
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| 66 | </tr> |
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| 67 | </thead> |
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| 68 | <tbody valign="top"> |
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| 69 | <tr class="row-even"><td>scale</td> |
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| 70 | <td>Source intensity</td> |
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| 71 | <td>None</td> |
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| 72 | <td>1</td> |
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| 73 | </tr> |
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| 74 | <tr class="row-odd"><td>background</td> |
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| 75 | <td>Source background</td> |
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| 76 | <td>cm<sup>-1</sup></td> |
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| 77 | <td>0</td> |
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| 78 | </tr> |
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| 79 | <tr class="row-even"><td>porod_scale</td> |
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| 80 | <td>Power law scale factor</td> |
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| 81 | <td>None</td> |
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| 82 | <td>1e-05</td> |
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| 83 | </tr> |
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| 84 | <tr class="row-odd"><td>porod_exp</td> |
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| 85 | <td>Exponent of power law</td> |
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| 86 | <td>None</td> |
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| 87 | <td>3</td> |
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| 88 | </tr> |
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| 89 | <tr class="row-even"><td>lorentz_scale</td> |
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| 90 | <td>Scale factor for broad Lorentzian peak</td> |
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| 91 | <td>None</td> |
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| 92 | <td>10</td> |
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| 93 | </tr> |
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| 94 | <tr class="row-odd"><td>lorentz_length</td> |
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| 95 | <td>Lorentzian screening length</td> |
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| 96 | <td>â«</td> |
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| 97 | <td>50</td> |
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| 98 | </tr> |
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| 99 | <tr class="row-even"><td>peak_pos</td> |
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| 100 | <td>Peak postion in q</td> |
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| 101 | <td>â«<sup>-1</sup></td> |
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| 102 | <td>0.1</td> |
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| 103 | </tr> |
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| 104 | <tr class="row-odd"><td>lorentz_exp</td> |
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| 105 | <td>exponent of Lorentz function</td> |
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| 106 | <td>None</td> |
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| 107 | <td>2</td> |
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| 108 | </tr> |
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| 109 | </tbody> |
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| 110 | </table> |
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| 111 | <p>The returned value is scaled to units of cm<sup>-1</sup>.</p> |
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| 112 | <p>This model calculates an empirical functional form for SAS data characterized |
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| 113 | by a broad scattering peak. Many SAS spectra are characterized by a broad peak |
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| 114 | even though they are from amorphous soft materials. For example, soft systems |
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| 115 | that show a SAS peak include copolymers, polyelectrolytes, multiphase systems, |
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| 116 | layered structures, etc.</p> |
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| 117 | <p>The d-spacing corresponding to the broad peak is a characteristic distance |
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| 118 | between the scattering inhomogeneities (such as in lamellar, cylindrical, or |
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| 119 | spherical morphologies, or for bicontinuous structures).</p> |
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| 120 | <p>The returned value is scaled to units of cm<sup>-1</sup>, absolute scale.</p> |
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| 121 | <div class="section" id="definition"> |
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| 122 | <h2>2.2.1.1. Definition<a class="headerlink" href="#definition" title="Permalink to this headline">¶</a></h2> |
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| 123 | <p>The scattering intensity <em>I(q)</em> is calculated as</p> |
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| 124 | <p>Here the peak position is related to the d-spacing as <em>Q0</em> = 2|pi| / <em>d0</em>.</p> |
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| 125 | <p>For 2D data: The 2D scattering intensity is calculated in the same way as 1D, |
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| 126 | where the <em>q</em> vector is defined as</p> |
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| 127 | <img alt="model/img/image175.jpg" src="model/img/image175.jpg" /> |
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| 128 | <p><em>Figure. 1D plot using the default values (w/200 data point).</em></p> |
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| 129 | </div> |
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| 130 | <div class="section" id="reference"> |
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| 131 | <h2>2.2.1.2. REFERENCE<a class="headerlink" href="#reference" title="Permalink to this headline">¶</a></h2> |
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| 132 | <p>None.</p> |
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| 133 | <p><em>2013/09/09 - Description reviewed by King, S and Parker, P.</em></p> |
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