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learn_thickness.html
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learn_thickness.html
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<!DOCTYPE html>
<html>
<head>
<title>Mosstool - Learn</title>
<link rel="icon" href="images/moessicon.png">
<link rel="stylesheet" type="text/css" href="css/moess_index.css">
<script type="text/javascript" src="js/learn_thickness.js"></script>
</head>
<body onload="" style="background-image: url(); background-size: 100%; background-position: right top; background-attachment: fixed;">
<ul class="topmenu_ul">
<div>
<li class="topmenu_ul"><img src="images/moessicon_v3b.png" alt="Mossbauer database" style="height:65px; float:left"></li>
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<div style="width:80%; margin-top: 0%; margin-left: 10%; background-color: white; opacity: 1">
<p style="text-align: right"><i>Published online: 12.06.2019 <br>Author: James M. Byrne</i></p>
</div>
<h4>Ideal Thickness Calculator</h4>
<div style="width:80%; margin-top: 0%; margin-left: 10%; background-color: white; opacity: 1">
<p>One of the challenges of preparing Mössbauer samples is knowing exactly how much material is needed to produce a decent spectrum with a good signal to noise ratio. Ultimately it comes down to having a suitable amount of Fe in your sample and the capacity of your sample holder. Below, we describe three methods for calculating the amount of sample you need for sample preparation:
<ol>
<li><a href="#stoichiometry" class="learnlink">Stoichiometry</a></li>
<li><a href="#weight%" class="learnlink">Fe wt%</a></li>
<li><a href="#concentration" class="learnlink">Fe concentration</a></li>
</ol>
<div id="stoichiometry" style="padding: 0px 0px 50px 0px; width:100%; margin-left: 0%;">
<b><h3>1. Stoichiometric formula</h3></b>
Based on the approximation suggested by Rancourt 1993, you can calculate the ideal thickness of your sample by entering the molecular formula, e.g. Fe3O4 and hitting Calculate below. The calculation uses mass absorption coefficients for each element at 14.4 keV taken from Gütlich et al. 2010.
</p>
<center>
<form action="javascript:" onsubmit="calculate(document.forms[0].elements[0].value)">
<input type=text size="20">
<input type=submit value="Calculate">
<input type=button onclick="document.forms[1].elements[0].value=''" value="Clear">
</form>
<form>
<textarea style="font-family:Arial" cols=45 rows=14></textarea>
</form>
</center>
<p>
This means that if you have a sample holder of 1 cm<sup>2</sup>, you should take the "Ideal thickness" as the mass you need to add to your sample holder. For our example of magnetite Fe3O4, the ideal thickness is 21.31 mg/cm<sup>2</sup> so you shoud add 21 mg of sample into a holder with area 1 cm<sup>2</sup>. In case you cannot create a nice homogenous thin layer when using such a small amount you can mix your sample with an Fe free unreactive compound such as glucose. For an example of a holder design, see our <a href="learn_prep.html" target="_blank">preparation</a> page.
</p>
</div>
<div id="weight%" style="padding: 0px 0px 50px 0px; width:100%; margin-left: 0%;">
<b><h3>2. Fe wt%</h3></b>
<p>
In some cases, the exact composition of the sample is unknown. This is not advisable because it suggests you have little idea about what is present within the sample which is a common mistake people make when trying to apply Mössbauer spectroscopy. A rough approximation can be made for how much sample is required based on the relative mass of Fe in the sample (i.e. wt%). Simply enter the Fe wt% (e.g. type 30 for 30 Fe wt%) in the box below and press Calculate.
</p>
<center>
Fe: <input type="text" style="width:80px; height:15px; margin-top:10px; margin-bottom:10px; padding: 5px 5px 5px 5px" id="wtcalc" placeholder="Enter mass" title="Weight"> wt%
<button onclick="wtpercent()">Calculate</button>
<br>Thickness: <input type="text" style="width:150px; height:15px; margin-top:10px; margin-bottom:10px; padding: 5px 5px 5px 5px" id="wtcalcresult" placeholder="" title="Weight"> mg/cm<sup>2</sup>
</center>
<p>
<b><i>Caution:</b> This calculation does not take into account the influence of other absorber atoms which might be present and can cause significant deviations from the calculated amount.</i>
</p>
</div>
<div id="concentration" style="padding: 0px 0px 50px 0px; width:100%; margin-left: 0%;">
<b><h3>3. Fe Concentration</h3></b>
<p>
Finally, lets assume you have a liquid and are preparing a sample through the filtration method described on the <a href="learn_prep.html" target="_blank">preparation</a> page. Now, we need to think in terms of the concentration of Fe present in your solution. The tool below will take that concentration (in mM) and make an approximation for the total volume of solution you need to use in order to prepare an "ideal" sample.
</p>
<center>
Concentration: <input type="text" style="width:80px; height:15px; margin-top:10px; margin-bottom:10px; padding: 5px 5px 5px 5px" id="liquid" placeholder="Enter conc." title="liquid"> mM
<button onclick="conc()">Calculate</button>
<br>Volume: <input type="text" style="width:150px; height:15px; margin-top:10px; margin-bottom:10px; padding: 5px 5px 5px 5px" id="concresult" placeholder="" title="conc"> ml
</center>
<p>
<b><i>Caution:</b> The filtration method is not perfect and it is not always possible to use the desired volume. If filters block easily, for example if you have a lot of organic matter, you should consider preparing several and making a stack. However, if you use too many filters, then your sample will deviate from the ideal thickness estimation so do not use more thana 3 stacked filters. Furthermore, this calculation does not take into account the influence of other absorber atoms which might be present and can cause significant deviations from the calculated amount.</i>
</p>
</div>
<h3>References</h3>
<ul>
<li>Rancourt D. G., McDonald A. M., Lalonde A. E., Ping J. Y., Mössbauer absorber thickness for accurate side populations in Fe-bearing minerals, 1993, <i>American Mineralogist</i>, Volume 78, </li>
<li>Gütlich, P., et al., Mössbauer spectroscopy and transition metal chemistry: fundamentals and applications. 2010, <i>Springer Science and Business Media</i></li>
</ul>
</body>
</html>