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<h1 id="firstHeading" class="firstHeading mw-first-heading"><span class="mw-page-title-main">Bethe-Formel</span></h1>
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<div id="mw-content-text" class="mw-body-content mw-content-ltr" lang="de" dir="ltr"><div class="mw-content-ltr mw-parser-output" lang="de" dir="ltr"><p>Die <b>Bethe-Formel</b> (auch <b>Bethe-Gleichung</b>, <b>Bethe-Bloch-Formel</b>, <b>Bethe-Bloch-Gleichung</b> oder <b>Bremsformel</b>) gibt den Energieverlust pro Weg an, den schnelle geladene schwere Teilchen (z.&nbsp;B. <a href="Proton" title="Proton">Protonen</a>, <a href="Alphastrahlung" title="Alphastrahlung">Alphateilchen</a>, <a href="Ion" title="Ion">Ionen</a>) beim Durchgang durch Materie durch inelastische Stöße mit den Elektronen erleiden; die übertragene Energie bewirkt im Material <a href="Angeregter_Zustand" title="Angeregter Zustand">Anregung</a> oder <a href="Sto%C3%9Fionisation" title="Stoßionisation">Ionisation</a>. Dieser Energieverlust, auch als <i>elektronische Abbremsung</i> oder ungenau als <b>Ionisationsverlust</b> bezeichnet, hängt ab von Geschwindigkeit und Ladung der Projektilteilchen und vom Targetmaterial.
</p><p>Die klassische nicht-<a href="Spezielle_Relativit%C3%A4tstheorie" title="Spezielle Relativitätstheorie">relativistische</a> Formel hat schon 1913 <a href="Niels_Bohr" title="Niels Bohr">Niels Bohr</a> aufgestellt<sup id="cite_ref-1" class="reference"><a href="#cite_note-1"><span class="cite-bracket">[</span>1<span class="cite-bracket">]</span></a></sup>, die quantenmechanisch nicht-relativistische Formel wurde dann 1930, die unten gezeigte quantenmechanisch-<a href="Spezielle_Relativit%C3%A4tstheorie" title="Spezielle Relativitätstheorie">relativistische</a> Version 1932 von <a href="Hans_Bethe" title="Hans Bethe">Hans Bethe</a> aufgestellt.<sup id="cite_ref-2" class="reference"><a href="#cite_note-2"><span class="cite-bracket">[</span>2<span class="cite-bracket">]</span></a></sup>
</p><p>Die Bethe-Bloch-Formel gilt <i>nicht</i> für einfallende Elektronen<sup id="cite_ref-3" class="reference"><a href="#cite_note-3"><span class="cite-bracket">[</span>3<span class="cite-bracket">]</span></a></sup>. Zum einen ist für diese der Energieverlust wegen ihrer <a href="Ununterscheidbarkeit" class="mw-redirect" title="Ununterscheidbarkeit">Ununterscheidbarkeit</a> mit den Hüllenelektronen des Materials anders. Zum anderen kommt bei Elektronen aufgrund ihrer geringen Masse ein bedeutender Energieverlust durch <a href="Bremsstrahlung" title="Bremsstrahlung">Bremsstrahlung</a> hinzu. Der Energieverlust von Elektronen kann stattdessen mit Hilfe der Berger-Seltzer-Formel beschrieben werden.<sup id="cite_ref-4" class="reference"><a href="#cite_note-4"><span class="cite-bracket">[</span>4<span class="cite-bracket">]</span></a></sup>
</p><p>Weitere Mechanismen, die zum Gesamt-Energieverlust schneller geladener schwerer Teilchen in Materie beitragen können, sind die nukleare Abbremsung (elastische Coulomb-Stöße mit den Atomkernen, siehe <a href="Bremsverm%C3%B6gen" title="Bremsvermögen">Bremsvermögen</a>) und die <a href="Bremsstrahlung" title="Bremsstrahlung">Bremsstrahlung</a>.
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<div class="mw-heading mw-heading2"><h2 id="Die_Formel">Die Formel</h2></div>

<p>Bewegen sich schnelle geladene Teilchen durch Materie, führen sie inelastische Stöße mit den Hüllenelektronen des Materials aus. Dies führt zur Anregung oder zur Ionisation der Atome. Dadurch erleidet das durchquerende Teilchen einen Energieverlust, der durch die folgende Formel näherungsweise angegeben wird. Ihre relativistische Form lautet:
</p>
<dl><dd><span class="mwe-math-element mwe-math-element-inline"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle -{\frac {\mathrm {d} E}{\mathrm {d} x}}={\frac {4\pi nz^{2}}{m_{\rm {e}}c^{2}\beta ^{2}}}\cdot \left({\frac {e^{2}}{4\pi \varepsilon _{0}}}\right)^{2}\cdot \left[\ln \left({\frac {2m_{\rm {e}}c^{2}\beta ^{2}}{I\cdot (1-\beta ^{2})}}\right)-\beta ^{2}\right]\qquad \qquad }">
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<annotation encoding="application/x-tex">{\displaystyle -{\frac {\mathrm {d} E}{\mathrm {d} x}}={\frac {4\pi nz^{2}}{m_{\rm {e}}c^{2}\beta ^{2}}}\cdot \left({\frac {e^{2}}{4\pi \varepsilon _{0}}}\right)^{2}\cdot \left[\ln \left({\frac {2m_{\rm {e}}c^{2}\beta ^{2}}{I\cdot (1-\beta ^{2})}}\right)-\beta ^{2}\right]\qquad \qquad }</annotation>
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</math></span><img src="./_assets_/eb734a37dd21ce173a46342d1cc64c92/9933ce49d06c6192caadf6f996ccd4ca456bd472.svg" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -2.671ex; width:64.632ex; height:6.843ex;" alt="{\displaystyle -{\frac {\mathrm {d} E}{\mathrm {d} x}}={\frac {4\pi nz^{2}}{m_{\rm {e}}c^{2}\beta ^{2}}}\cdot \left({\frac {e^{2}}{4\pi \varepsilon _{0}}}\right)^{2}\cdot \left[\ln \left({\frac {2m_{\rm {e}}c^{2}\beta ^{2}}{I\cdot (1-\beta ^{2})}}\right)-\beta ^{2}\right]\qquad \qquad }" loading="lazy"></span> (1)</dd></dl>
<p>wobei
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<td><span class="mwe-math-element mwe-math-element-inline"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle \beta }">
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<td>= <span class="mwe-math-element mwe-math-element-inline"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle v/c}">
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</math></span><img src="./_assets_/eb734a37dd21ce173a46342d1cc64c92/bd5fbfe05e197127354e233f6c813e6b5d846672.svg" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.838ex; width:3.297ex; height:2.843ex;" alt="{\displaystyle v/c}" loading="lazy"></span>
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<td><span class="mwe-math-element mwe-math-element-inline"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle v}">
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<td>= momentane Geschwindigkeit des Teilchens
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<td><span class="mwe-math-element mwe-math-element-inline"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle c}">
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<mi>c</mi>
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<td>= Lichtgeschwindigkeit
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<td><span class="mwe-math-element mwe-math-element-inline"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle E}">
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<td>= Energie des Teilchens
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<td><span class="mwe-math-element mwe-math-element-inline"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle x}">
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</math></span><img src="./_assets_/eb734a37dd21ce173a46342d1cc64c92/87f9e315fd7e2ba406057a97300593c4802b53e4.svg" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.338ex; width:1.33ex; height:1.676ex;" alt="{\displaystyle x}" loading="lazy"></span>
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<td>= Weglänge
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<td><span class="mwe-math-element mwe-math-element-inline"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle z}">
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<td>= Ladungszahl des Teilchens (<span class="mwe-math-element mwe-math-element-inline"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle z\cdot e}">
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</math></span><img src="./_assets_/eb734a37dd21ce173a46342d1cc64c92/80efe61f2ae9bd81f5338f383238b1595841c816.svg" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.338ex; width:3.851ex; height:1.676ex;" alt="{\displaystyle z\cdot e}" loading="lazy"></span> = Ladung des Teilchens)
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<td><span class="mwe-math-element mwe-math-element-inline"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle \varepsilon _{0}}">
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<annotation encoding="application/x-tex">{\displaystyle \varepsilon _{0}}</annotation>
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<td>= <a href="Elektrische_Feldkonstante" title="Elektrische Feldkonstante">Elektrische Feldkonstante</a>
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<td><span class="mwe-math-element mwe-math-element-inline"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle e}">
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<td>= Elementarladung
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<td><span class="mwe-math-element mwe-math-element-inline"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle n}">
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</math></span><img src="./_assets_/eb734a37dd21ce173a46342d1cc64c92/a601995d55609f2d9f5e233e36fbe9ea26011b3b.svg" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.338ex; width:1.395ex; height:1.676ex;" alt="{\displaystyle n}" loading="lazy"></span>
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<td>= Elektronendichte des Materials
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<td><span class="mwe-math-element mwe-math-element-inline"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle m_{\rm {e}}}">
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<mi>m</mi>
<mrow class="MJX-TeXAtom-ORD">
<mrow class="MJX-TeXAtom-ORD">
<mi mathvariant="normal">e</mi>
</mrow>
</mrow>
</msub>
</mstyle>
</mrow>
<annotation encoding="application/x-tex">{\displaystyle m_{\rm {e}}}</annotation>
</semantics>
</math></span><img src="./_assets_/eb734a37dd21ce173a46342d1cc64c92/7b851e51e5663a2a922853bdbf69003072950aef.svg" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.671ex; width:3.003ex; height:2.009ex;" alt="{\displaystyle m_{\rm {e}}}" loading="lazy"></span>
</td>
<td>= Masse des Elektrons
</td></tr>
<tr>
<td><span class="mwe-math-element mwe-math-element-inline"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle I}">
<semantics>
<mrow class="MJX-TeXAtom-ORD">
<mstyle displaystyle="true" scriptlevel="0">
<mi>I</mi>
</mstyle>
</mrow>
<annotation encoding="application/x-tex">{\displaystyle I}</annotation>
</semantics>
</math></span><img src="./_assets_/eb734a37dd21ce173a46342d1cc64c92/535ea7fc4134a31cbe2251d9d3511374bc41be9f.svg" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.338ex; width:1.172ex; height:2.176ex;" alt="{\displaystyle I}" loading="lazy"></span>
</td>
<td>= mittleres Anregungspotential des Materials (<a href="#Das_mittlere_Anregungspotential">s.&nbsp;u.</a>)
</td></tr></tbody></table>
<p>Die Elektronendichte <span class="mwe-math-element mwe-math-element-inline"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle n}">
<semantics>
<mrow class="MJX-TeXAtom-ORD">
<mstyle displaystyle="true" scriptlevel="0">
<mi>n</mi>
</mstyle>
</mrow>
<annotation encoding="application/x-tex">{\displaystyle n}</annotation>
</semantics>
</math></span><img src="./_assets_/eb734a37dd21ce173a46342d1cc64c92/a601995d55609f2d9f5e233e36fbe9ea26011b3b.svg" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.338ex; width:1.395ex; height:1.676ex;" alt="{\displaystyle n}" loading="lazy"></span> lässt sich dabei mit <span class="mwe-math-element mwe-math-element-inline"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle n={\frac {Z\cdot \rho }{A\cdot u}}}">
<semantics>
<mrow class="MJX-TeXAtom-ORD">
<mstyle displaystyle="true" scriptlevel="0">
<mi>n</mi>
<mo>=</mo>
<mrow class="MJX-TeXAtom-ORD">
<mfrac>
<mrow>
<mi>Z</mi>
<mo>⋅<!-- ⋅ --></mo>
<mi>ρ<!-- ρ --></mi>
</mrow>
<mrow>
<mi>A</mi>
<mo>⋅<!-- ⋅ --></mo>
<mi>u</mi>
</mrow>
</mfrac>
</mrow>
</mstyle>
</mrow>
<annotation encoding="application/x-tex">{\displaystyle n={\frac {Z\cdot \rho }{A\cdot u}}}</annotation>
</semantics>
</math></span><img src="./_assets_/eb734a37dd21ce173a46342d1cc64c92/f34a697f42144b48dae31b26103f47e0afcbeebb.svg" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -2.005ex; width:10.081ex; height:5.509ex;" alt="{\displaystyle n={\frac {Z\cdot \rho }{A\cdot u}}}" loading="lazy"></span> berechnen; <span class="mwe-math-element mwe-math-element-inline"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle \rho }">
<semantics>
<mrow class="MJX-TeXAtom-ORD">
<mstyle displaystyle="true" scriptlevel="0">
<mi>ρ<!-- ρ --></mi>
</mstyle>
</mrow>
<annotation encoding="application/x-tex">{\displaystyle \rho }</annotation>
</semantics>
</math></span><img src="./_assets_/eb734a37dd21ce173a46342d1cc64c92/1f7d439671d1289b6a816e6af7a304be40608d64.svg" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.838ex; width:1.202ex; height:2.176ex;" alt="{\displaystyle \rho }" loading="lazy"></span> ist die Dichte des Materials, <span class="mwe-math-element mwe-math-element-inline"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle Z}">
<semantics>
<mrow class="MJX-TeXAtom-ORD">
<mstyle displaystyle="true" scriptlevel="0">
<mi>Z</mi>
</mstyle>
</mrow>
<annotation encoding="application/x-tex">{\displaystyle Z}</annotation>
</semantics>
</math></span><img src="./_assets_/eb734a37dd21ce173a46342d1cc64c92/1cc6b75e09a8aa3f04d8584b11db534f88fb56bd.svg" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.338ex; width:1.68ex; height:2.176ex;" alt="{\displaystyle Z}" loading="lazy"></span> und <span class="mwe-math-element mwe-math-element-inline"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle A}">
<semantics>
<mrow class="MJX-TeXAtom-ORD">
<mstyle displaystyle="true" scriptlevel="0">
<mi>A</mi>
</mstyle>
</mrow>
<annotation encoding="application/x-tex">{\displaystyle A}</annotation>
</semantics>
</math></span><img src="./_assets_/eb734a37dd21ce173a46342d1cc64c92/7daff47fa58cdfd29dc333def748ff5fa4c923e3.svg" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.338ex; width:1.743ex; height:2.176ex;" alt="{\displaystyle A}" loading="lazy"></span> Ordnungs- bzw. Massenzahl des Materials und <span class="mwe-math-element mwe-math-element-inline"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle u}">
<semantics>
<mrow class="MJX-TeXAtom-ORD">
<mstyle displaystyle="true" scriptlevel="0">
<mi>u</mi>
</mstyle>
</mrow>
<annotation encoding="application/x-tex">{\displaystyle u}</annotation>
</semantics>
</math></span><img src="./_assets_/eb734a37dd21ce173a46342d1cc64c92/c3e6bb763d22c20916ed4f0bb6bd49d7470cffd8.svg" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.338ex; width:1.33ex; height:1.676ex;" alt="{\displaystyle u}" loading="lazy"></span> die <a href="Atomare_Masseneinheit" title="Atomare Masseneinheit">atomare Masseneinheit</a>.
</p><p>Im Bild rechts bedeuten die kleinen Kreise Messergebnisse von verschiedenen Arbeitsgruppen<sup id="cite_ref-5" class="reference"><a href="#cite_note-5"><span class="cite-bracket">[</span>5<span class="cite-bracket">]</span></a></sup>; die rote Kurve stellt die Bethe-Formel dar. Offenbar ist die Übereinstimmung von Bethes Theorie mit den Experimenten oberhalb von 0,5&nbsp;MeV sehr gut, besonders wenn die Korrekturen (s.&nbsp;u.) hinzugefügt werden (blaue Kurve).
</p><p>Für kleine Energien, d.&nbsp;h. kleine Teilchengeschwindigkeiten <span class="mwe-math-element mwe-math-element-inline"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle (\beta \ll 1)}">
<semantics>
<mrow class="MJX-TeXAtom-ORD">
<mstyle displaystyle="true" scriptlevel="0">
<mo stretchy="false">(</mo>
<mi>β<!-- β --></mi>
<mo>≪<!-- ≪ --></mo>
<mn>1</mn>
<mo stretchy="false">)</mo>
</mstyle>
</mrow>
<annotation encoding="application/x-tex">{\displaystyle (\beta \ll 1)}</annotation>
</semantics>
</math></span><img src="./_assets_/eb734a37dd21ce173a46342d1cc64c92/d4ef1c145ae273e78234c0fb7ed32164f7c7439a.svg" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.838ex; width:7.918ex; height:2.843ex;" alt="{\displaystyle (\beta \ll 1)}" loading="lazy"></span>, reduziert sich die Bethe-Formel auf
</p>
<dl><dd><span class="mwe-math-element mwe-math-element-inline"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle -{\frac {\mathrm {d} E}{\mathrm {d} x}}={\frac {4\pi nz^{2}}{m_{e}v^{2}}}\cdot \left({\frac {e^{2}}{4\pi \varepsilon _{0}}}\right)^{2}\cdot \ln \left({\frac {2m_{e}v^{2}}{I}}\right).}">
<semantics>
<mrow class="MJX-TeXAtom-ORD">
<mstyle displaystyle="true" scriptlevel="0">
<mo>−<!-- − --></mo>
<mrow class="MJX-TeXAtom-ORD">
<mfrac>
<mrow>
<mrow class="MJX-TeXAtom-ORD">
<mi mathvariant="normal">d</mi>
</mrow>
<mi>E</mi>
</mrow>
<mrow>
<mrow class="MJX-TeXAtom-ORD">
<mi mathvariant="normal">d</mi>
</mrow>
<mi>x</mi>
</mrow>
</mfrac>
</mrow>
<mo>=</mo>
<mrow class="MJX-TeXAtom-ORD">
<mfrac>
<mrow>
<mn>4</mn>
<mi>π<!-- π --></mi>
<mi>n</mi>
<msup>
<mi>z</mi>
<mrow class="MJX-TeXAtom-ORD">
<mn>2</mn>
</mrow>
</msup>
</mrow>
<mrow>
<msub>
<mi>m</mi>
<mrow class="MJX-TeXAtom-ORD">
<mi>e</mi>
</mrow>
</msub>
<msup>
<mi>v</mi>
<mrow class="MJX-TeXAtom-ORD">
<mn>2</mn>
</mrow>
</msup>
</mrow>
</mfrac>
</mrow>
<mo>⋅<!-- ⋅ --></mo>
<msup>
<mrow>
<mo>(</mo>
<mrow class="MJX-TeXAtom-ORD">
<mfrac>
<msup>
<mi>e</mi>
<mrow class="MJX-TeXAtom-ORD">
<mn>2</mn>
</mrow>
</msup>
<mrow>
<mn>4</mn>
<mi>π<!-- π --></mi>
<msub>
<mi>ε<!-- ε --></mi>
<mrow class="MJX-TeXAtom-ORD">
<mn>0</mn>
</mrow>
</msub>
</mrow>
</mfrac>
</mrow>
<mo>)</mo>
</mrow>
<mrow class="MJX-TeXAtom-ORD">
<mn>2</mn>
</mrow>
</msup>
<mo>⋅<!-- ⋅ --></mo>
<mi>ln</mi>
<mo>⁡<!-- ⁡ --></mo>
<mrow>
<mo>(</mo>
<mrow class="MJX-TeXAtom-ORD">
<mfrac>
<mrow>
<mn>2</mn>
<msub>
<mi>m</mi>
<mrow class="MJX-TeXAtom-ORD">
<mi>e</mi>
</mrow>
</msub>
<msup>
<mi>v</mi>
<mrow class="MJX-TeXAtom-ORD">
<mn>2</mn>
</mrow>
</msup>
</mrow>
<mi>I</mi>
</mfrac>
</mrow>
<mo>)</mo>
</mrow>
<mo>.</mo>
</mstyle>
</mrow>
<annotation encoding="application/x-tex">{\displaystyle -{\frac {\mathrm {d} E}{\mathrm {d} x}}={\frac {4\pi nz^{2}}{m_{e}v^{2}}}\cdot \left({\frac {e^{2}}{4\pi \varepsilon _{0}}}\right)^{2}\cdot \ln \left({\frac {2m_{e}v^{2}}{I}}\right).}</annotation>
</semantics>
</math></span><img src="./_assets_/eb734a37dd21ce173a46342d1cc64c92/b00592047ed9a424a3d8eb4826dbfb146550815a.svg" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -2.505ex; width:42.209ex; height:6.676ex;" alt="{\displaystyle -{\frac {\mathrm {d} E}{\mathrm {d} x}}={\frac {4\pi nz^{2}}{m_{e}v^{2}}}\cdot \left({\frac {e^{2}}{4\pi \varepsilon _{0}}}\right)^{2}\cdot \ln \left({\frac {2m_{e}v^{2}}{I}}\right).}" loading="lazy"></span></dd></dl>
<p>Bei kleinen Energien ist die Bethe-Formel nur dann gültig, wenn diese noch hoch genug sind, dass das durchquerende Teilchen keine Hüllenelektronen mit sich führt. Anderenfalls wird seine effektive Ladung dadurch reduziert, und das Bremsvermögen ist kleiner. Es gibt für kleine Energien eine verfeinerte Theorie der elektronischen Abbremsung von Jens Lindhard, Morten Scharff und Hans E. Schiøtt (<a href="LSS-Theorie" title="LSS-Theorie">LSS-Theorie</a>)<sup id="cite_ref-6" class="reference"><a href="#cite_note-6"><span class="cite-bracket">[</span>6<span class="cite-bracket">]</span></a></sup>. Näherungsweise wird auch die Barkas-Formel<sup id="cite_ref-7" class="reference"><a href="#cite_note-7"><span class="cite-bracket">[</span>7<span class="cite-bracket">]</span></a></sup> für die effektive Ladungszahl benutzt:
</p>
<dl><dd><span class="mwe-math-element mwe-math-element-inline"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle z_{\mathrm {eff} }=z\left(1-\exp \left(-125\beta z^{-{\frac {2}{3}}}\right)\right)}">
<semantics>
<mrow class="MJX-TeXAtom-ORD">
<mstyle displaystyle="true" scriptlevel="0">
<msub>
<mi>z</mi>
<mrow class="MJX-TeXAtom-ORD">
<mrow class="MJX-TeXAtom-ORD">
<mi mathvariant="normal">e</mi>
<mi mathvariant="normal">f</mi>
<mi mathvariant="normal">f</mi>
</mrow>
</mrow>
</msub>
<mo>=</mo>
<mi>z</mi>
<mrow>
<mo>(</mo>
<mrow>
<mn>1</mn>
<mo>−<!-- − --></mo>
<mi>exp</mi>
<mo>⁡<!-- ⁡ --></mo>
<mrow>
<mo>(</mo>
<mrow>
<mo>−<!-- − --></mo>
<mn>125</mn>
<mi>β<!-- β --></mi>
<msup>
<mi>z</mi>
<mrow class="MJX-TeXAtom-ORD">
<mo>−<!-- − --></mo>
<mrow class="MJX-TeXAtom-ORD">
<mfrac>
<mn>2</mn>
<mn>3</mn>
</mfrac>
</mrow>
</mrow>
</msup>
</mrow>
<mo>)</mo>
</mrow>
</mrow>
<mo>)</mo>
</mrow>
</mstyle>
</mrow>
<annotation encoding="application/x-tex">{\displaystyle z_{\mathrm {eff} }=z\left(1-\exp \left(-125\beta z^{-{\frac {2}{3}}}\right)\right)}</annotation>
</semantics>
</math></span><img src="./_assets_/eb734a37dd21ce173a46342d1cc64c92/36568e3c7a848da83e1a2f8a5a15bf426c7cecfd.svg" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -2.505ex; width:32.97ex; height:6.176ex;" alt="{\displaystyle z_{\mathrm {eff} }=z\left(1-\exp \left(-125\beta z^{-{\frac {2}{3}}}\right)\right)}" loading="lazy"></span></dd></dl>
<p>Allgemein fällt der Energieverlust mit steigender Energie zunächst etwa mit <span class="mwe-math-element mwe-math-element-inline"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle 1/v^{2}}">
<semantics>
<mrow class="MJX-TeXAtom-ORD">
<mstyle displaystyle="true" scriptlevel="0">
<mn>1</mn>
<mrow class="MJX-TeXAtom-ORD">
<mo>/</mo>
</mrow>
<msup>
<mi>v</mi>
<mrow class="MJX-TeXAtom-ORD">
<mn>2</mn>
</mrow>
</msup>
</mstyle>
</mrow>
<annotation encoding="application/x-tex">{\displaystyle 1/v^{2}}</annotation>
</semantics>
</math></span><img src="./_assets_/eb734a37dd21ce173a46342d1cc64c92/d129604233f925dee796f1dccea48ef4e236e6d4.svg" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.838ex; width:4.507ex; height:3.176ex;" alt="{\displaystyle 1/v^{2}}" loading="lazy"></span> ab und erreicht ein Minimum bei etwa <span class="mwe-math-element mwe-math-element-inline"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle E=3m_{T}c^{2}}">
<semantics>
<mrow class="MJX-TeXAtom-ORD">
<mstyle displaystyle="true" scriptlevel="0">
<mi>E</mi>
<mo>=</mo>
<mn>3</mn>
<msub>
<mi>m</mi>
<mrow class="MJX-TeXAtom-ORD">
<mi>T</mi>
</mrow>
</msub>
<msup>
<mi>c</mi>
<mrow class="MJX-TeXAtom-ORD">
<mn>2</mn>
</mrow>
</msup>
</mstyle>
</mrow>
<annotation encoding="application/x-tex">{\displaystyle E=3m_{T}c^{2}}</annotation>
</semantics>
</math></span><img src="./_assets_/eb734a37dd21ce173a46342d1cc64c92/62e9df5880ae978a6c4e2646f4d53ad8eeebc1d4.svg" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.671ex; width:11.527ex; height:3.009ex;" alt="{\displaystyle E=3m_{T}c^{2}}" loading="lazy"></span>, wobei <span class="mwe-math-element mwe-math-element-inline"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle m_{T}}">
<semantics>
<mrow class="MJX-TeXAtom-ORD">
<mstyle displaystyle="true" scriptlevel="0">
<msub>
<mi>m</mi>
<mrow class="MJX-TeXAtom-ORD">
<mi>T</mi>
</mrow>
</msub>
</mstyle>
</mrow>
<annotation encoding="application/x-tex">{\displaystyle m_{T}}</annotation>
</semantics>
</math></span><img src="./_assets_/eb734a37dd21ce173a46342d1cc64c92/2767d339e0bb9818b1057574bed41e54d9ece4d7.svg" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.671ex; width:3.43ex; height:2.009ex;" alt="{\displaystyle m_{T}}" loading="lazy"></span> die Masse des Teilchens ist (also z.&nbsp;B. für Protonen etwa bei 3&nbsp;GeV, was im Bild nicht mehr sichtbar ist). Da für viele in der <a href="Teilchenphysik" title="Teilchenphysik">Teilchenphysik</a> relevante Strahlungsteilchen und Absorbermaterialien der Energieverlust in der Nähe des Minimums ungefähr den gleichen Wert hat, werden Teilchen mit einer Energie in der Nähe des Minimums häufig zusammengefasst und als MIPs (<span lang="en"><i>Minimum Ionizing Particles</i></span>, dt. <i>minimal ionisierende Teilchen</i>) bezeichnet. Als Faustformel für den spezifischen Energieverlust der MIPs gilt:
</p>
<dl><dd><span class="mwe-math-element mwe-math-element-inline"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle -{\frac {1}{\rho }}{\frac {\mathrm {d} E}{\mathrm {d} x}}\approx 2{\frac {\mathrm {MeV} \mathrm {cm} ^{2}}{\mathrm {g} \;}}}">
<semantics>
<mrow class="MJX-TeXAtom-ORD">
<mstyle displaystyle="true" scriptlevel="0">
<mo>−<!-- − --></mo>
<mrow class="MJX-TeXAtom-ORD">
<mfrac>
<mn>1</mn>
<mi>ρ<!-- ρ --></mi>
</mfrac>
</mrow>
<mrow class="MJX-TeXAtom-ORD">
<mfrac>
<mrow>
<mrow class="MJX-TeXAtom-ORD">
<mi mathvariant="normal">d</mi>
</mrow>
<mi>E</mi>
</mrow>
<mrow>
<mrow class="MJX-TeXAtom-ORD">
<mi mathvariant="normal">d</mi>
</mrow>
<mi>x</mi>
</mrow>
</mfrac>
</mrow>
<mo>≈<!-- ≈ --></mo>
<mn>2</mn>
<mrow class="MJX-TeXAtom-ORD">
<mfrac>
<mrow>
<mrow class="MJX-TeXAtom-ORD">
<mi mathvariant="normal">M</mi>
<mi mathvariant="normal">e</mi>
<mi mathvariant="normal">V</mi>
</mrow>
<msup>
<mrow class="MJX-TeXAtom-ORD">
<mi mathvariant="normal">c</mi>
<mi mathvariant="normal">m</mi>
</mrow>
<mrow class="MJX-TeXAtom-ORD">
<mn>2</mn>
</mrow>
</msup>
</mrow>
<mrow>
<mrow class="MJX-TeXAtom-ORD">
<mi mathvariant="normal">g</mi>
</mrow>
<mspace width="thickmathspace"></mspace>
</mrow>
</mfrac>
</mrow>
</mstyle>
</mrow>
<annotation encoding="application/x-tex">{\displaystyle -{\frac {1}{\rho }}{\frac {\mathrm {d} E}{\mathrm {d} x}}\approx 2{\frac {\mathrm {MeV} \mathrm {cm} ^{2}}{\mathrm {g} \;}}}</annotation>
</semantics>
</math></span><img src="./_assets_/eb734a37dd21ce173a46342d1cc64c92/e110aa9fbf3740593e7f111739aa85dfaf6393d0.svg" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -2.338ex; width:21.777ex; height:6.176ex;" alt="{\displaystyle -{\frac {1}{\rho }}{\frac {\mathrm {d} E}{\mathrm {d} x}}\approx 2{\frac {\mathrm {MeV} \mathrm {cm} ^{2}}{\mathrm {g} \;}}}" loading="lazy"></span><sup id="cite_ref-8" class="reference"><a href="#cite_note-8"><span class="cite-bracket">[</span>8<span class="cite-bracket">]</span></a></sup>.</dd></dl>
<p>Bei noch höherer Energie steigt der Energieverlust wieder an. Bei sehr hohen Energien müssen auch Teilchen<i>reaktionen</i> berücksichtigt werden, die zu Sekundärteilchen führen. Der Energieverlust kann daher in materialabhängiger Weise noch stärker ansteigen.
</p><p>In der <a href="Strahlenbiologie" title="Strahlenbiologie">Strahlenbiologie</a> nennt man die Energieabgabe ionisierender Teilchen gemäß der Bethe-Bloch-Gleichung den <a href="Linearer_Energietransfer" title="Linearer Energietransfer">Linearen Energietransfer</a> (<span class="mwe-math-element mwe-math-element-inline"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle LET_{\infty }}">
<semantics>
<mrow class="MJX-TeXAtom-ORD">
<mstyle displaystyle="true" scriptlevel="0">
<mi>L</mi>
<mi>E</mi>
<msub>
<mi>T</mi>
<mrow class="MJX-TeXAtom-ORD">
<mi mathvariant="normal">∞<!-- ∞ --></mi>
</mrow>
</msub>
</mstyle>
</mrow>
<annotation encoding="application/x-tex">{\displaystyle LET_{\infty }}</annotation>
</semantics>
</math></span><img src="./_assets_/eb734a37dd21ce173a46342d1cc64c92/85ce118261520d8bf9b936631244187283061aa7.svg" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.671ex; width:6.591ex; height:2.509ex;" alt="{\displaystyle LET_{\infty }}" loading="lazy"></span>) und verwendet die Einheit Kiloelektronenvolt pro Mikrometer (keV/µm).
</p>
<div class="mw-heading mw-heading2"><h2 id="Das_mittlere_Anregungspotential">Das mittlere Anregungspotential</h2></div>
<p>Im Gültigkeitsbereich der Bethe-Formel (1) wird das durchdrungene Material neben der Teilchendichte <span class="mwe-math-element mwe-math-element-inline"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle n}">
<semantics>
<mrow class="MJX-TeXAtom-ORD">
<mstyle displaystyle="true" scriptlevel="0">
<mi>n</mi>
</mstyle>
</mrow>
<annotation encoding="application/x-tex">{\displaystyle n}</annotation>
</semantics>
</math></span><img src="./_assets_/eb734a37dd21ce173a46342d1cc64c92/a601995d55609f2d9f5e233e36fbe9ea26011b3b.svg" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.338ex; width:1.395ex; height:1.676ex;" alt="{\displaystyle n}" loading="lazy"></span> nur durch eine einzige Konstante, das mittlere Anregungspotential <span class="mwe-math-element mwe-math-element-inline"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle I}">
<semantics>
<mrow class="MJX-TeXAtom-ORD">
<mstyle displaystyle="true" scriptlevel="0">
<mi>I</mi>
</mstyle>
</mrow>
<annotation encoding="application/x-tex">{\displaystyle I}</annotation>
</semantics>
</math></span><img src="./_assets_/eb734a37dd21ce173a46342d1cc64c92/535ea7fc4134a31cbe2251d9d3511374bc41be9f.svg" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.338ex; width:1.172ex; height:2.176ex;" alt="{\displaystyle I}" loading="lazy"></span>, beschrieben.
</p><p><a href="Felix_Bloch_(Physiker)" class="mw-redirect" title="Felix Bloch (Physiker)">Felix Bloch</a> hat 1933 gezeigt<sup id="cite_ref-9" class="reference"><a href="#cite_note-9"><span class="cite-bracket">[</span>9<span class="cite-bracket">]</span></a></sup>, dass das mittlere Anregungspotential der Atome im Mittel etwa
</p>
<dl><dd><span class="mwe-math-element mwe-math-element-inline"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle I=(10\,\mathrm {eV} )\cdot Z\qquad \qquad }">
<semantics>
<mrow class="MJX-TeXAtom-ORD">
<mstyle displaystyle="true" scriptlevel="0">
<mi>I</mi>
<mo>=</mo>
<mo stretchy="false">(</mo>
<mn>10</mn>
<mspace width="thinmathspace"></mspace>
<mrow class="MJX-TeXAtom-ORD">
<mi mathvariant="normal">e</mi>
<mi mathvariant="normal">V</mi>
</mrow>
<mo stretchy="false">)</mo>
<mo>⋅<!-- ⋅ --></mo>
<mi>Z</mi>
<mspace width="2em"></mspace>
<mspace width="2em"></mspace>
</mstyle>
</mrow>
<annotation encoding="application/x-tex">{\displaystyle I=(10\,\mathrm {eV} )\cdot Z\qquad \qquad }</annotation>
</semantics>
</math></span><img src="./_assets_/eb734a37dd21ce173a46342d1cc64c92/93f4ea22d4bae70442f982dd13c507a464b8d6f6.svg" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.838ex; width:24.217ex; height:2.843ex;" alt="{\displaystyle I=(10\,\mathrm {eV} )\cdot Z\qquad \qquad }" loading="lazy"></span> (2)</dd></dl>
<p>beträgt, wo <span class="mwe-math-element mwe-math-element-inline"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle Z}">
<semantics>
<mrow class="MJX-TeXAtom-ORD">
<mstyle displaystyle="true" scriptlevel="0">
<mi>Z</mi>
</mstyle>
</mrow>
<annotation encoding="application/x-tex">{\displaystyle Z}</annotation>
</semantics>
</math></span><img src="./_assets_/eb734a37dd21ce173a46342d1cc64c92/1cc6b75e09a8aa3f04d8584b11db534f88fb56bd.svg" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.338ex; width:1.68ex; height:2.176ex;" alt="{\displaystyle Z}" loading="lazy"></span> die <a href="Ordnungszahl" title="Ordnungszahl">Ordnungszahl</a> der Atome des Materials bedeutet. Setzt man diese Größe in Formel (1) oben ein, so führt das zu einer Gleichung, die oft als <i>Bethe-Bloch-Gleichung</i> bezeichnet wird. Es gibt aber genauere Tabellen<sup id="cite_ref-ICRU49_10-0" class="reference"><a href="#cite_note-ICRU49-10"><span class="cite-bracket">[</span>10<span class="cite-bracket">]</span></a></sup> von <span class="mwe-math-element mwe-math-element-inline"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle I}">
<semantics>
<mrow class="MJX-TeXAtom-ORD">
<mstyle displaystyle="true" scriptlevel="0">
<mi>I</mi>
</mstyle>
</mrow>
<annotation encoding="application/x-tex">{\displaystyle I}</annotation>
</semantics>
</math></span><img src="./_assets_/eb734a37dd21ce173a46342d1cc64c92/535ea7fc4134a31cbe2251d9d3511374bc41be9f.svg" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.338ex; width:1.172ex; height:2.176ex;" alt="{\displaystyle I}" loading="lazy"></span> als Funktion von <span class="mwe-math-element mwe-math-element-inline"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle Z}">
<semantics>
<mrow class="MJX-TeXAtom-ORD">
<mstyle displaystyle="true" scriptlevel="0">
<mi>Z</mi>
</mstyle>
</mrow>
<annotation encoding="application/x-tex">{\displaystyle Z}</annotation>
</semantics>
</math></span><img src="./_assets_/eb734a37dd21ce173a46342d1cc64c92/1cc6b75e09a8aa3f04d8584b11db534f88fb56bd.svg" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.338ex; width:1.68ex; height:2.176ex;" alt="{\displaystyle Z}" loading="lazy"></span>. Mit ihnen erhält man bessere Resultate als mit Formel (2).
</p>
<p> Im Bild ist das mittlere Anregungspotential der verschiedenen Elemente gezeigt, das die Information über das jeweilige Atom enthält. Die Daten stammen aus dem genannten ICRU-Report.<sup id="cite_ref-ICRU49_10-1" class="reference"><a href="#cite_note-ICRU49-10"><span class="cite-bracket">[</span>10<span class="cite-bracket">]</span></a></sup> Den Spitzen und Tälern in der Darstellung („<span class="mwe-math-element mwe-math-element-inline"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle Z_{2}}">
<semantics>
<mrow class="MJX-TeXAtom-ORD">
<mstyle displaystyle="true" scriptlevel="0">
<msub>
<mi>Z</mi>
<mrow class="MJX-TeXAtom-ORD">
<mn>2</mn>
</mrow>
</msub>
</mstyle>
</mrow>
<annotation encoding="application/x-tex">{\displaystyle Z_{2}}</annotation>
</semantics>
</math></span><img src="./_assets_/eb734a37dd21ce173a46342d1cc64c92/c98d433ae289ecb2b88f895b407538b0e4183b28.svg" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.671ex; width:2.642ex; height:2.509ex;" alt="{\displaystyle Z_{2}}" loading="lazy"></span>-Oszillationen“, wobei <span class="mwe-math-element mwe-math-element-inline"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle Z_{2}}">
<semantics>
<mrow class="MJX-TeXAtom-ORD">
<mstyle displaystyle="true" scriptlevel="0">
<msub>
<mi>Z</mi>
<mrow class="MJX-TeXAtom-ORD">
<mn>2</mn>
</mrow>
</msub>
</mstyle>
</mrow>
<annotation encoding="application/x-tex">{\displaystyle Z_{2}}</annotation>
</semantics>
</math></span><img src="./_assets_/eb734a37dd21ce173a46342d1cc64c92/c98d433ae289ecb2b88f895b407538b0e4183b28.svg" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.671ex; width:2.642ex; height:2.509ex;" alt="{\displaystyle Z_{2}}" loading="lazy"></span> die Ordnungszahl des Materials bedeutet) entsprechen niedrigere bzw. höhere Werte des Bremsvermögens; diese Oszillationen beruhen auf der <a href="Schalenmodell_(Atomphysik)" title="Schalenmodell (Atomphysik)">Schalenstruktur</a> der Atome. Wie das Bild zeigt, gilt Formel (2) nur näherungsweise.
</p><div class="mw-heading mw-heading2"><h2 id="Korrekturen">Korrekturen</h2></div>
<p>Die Bethe-Formel wurde von Bethe mit Hilfe der <a href="Quantenmechanik" title="Quantenmechanik">quantenmechanischen</a> <a href="St%C3%B6rungstheorie_(Quantenmechanik)" title="Störungstheorie (Quantenmechanik)">Störungstheorie</a> abgeleitet, das Ergebnis ist daher dem Quadrat der Ladung <span class="mwe-math-element mwe-math-element-inline"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle z}">
<semantics>
<mrow class="MJX-TeXAtom-ORD">
<mstyle displaystyle="true" scriptlevel="0">
<mi>z</mi>
</mstyle>
</mrow>
<annotation encoding="application/x-tex">{\displaystyle z}</annotation>
</semantics>
</math></span><img src="./_assets_/eb734a37dd21ce173a46342d1cc64c92/bf368e72c009decd9b6686ee84a375632e11de98.svg" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.338ex; width:1.088ex; height:1.676ex;" alt="{\displaystyle z}" loading="lazy"></span> proportional. Eine bessere Beschreibung erhält man, wenn man auch Abweichungen berücksichtigt, die höheren Potenzen von <span class="mwe-math-element mwe-math-element-inline"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle z}">
<semantics>
<mrow class="MJX-TeXAtom-ORD">
<mstyle displaystyle="true" scriptlevel="0">
<mi>z</mi>
</mstyle>
</mrow>
<annotation encoding="application/x-tex">{\displaystyle z}</annotation>
</semantics>
</math></span><img src="./_assets_/eb734a37dd21ce173a46342d1cc64c92/bf368e72c009decd9b6686ee84a375632e11de98.svg" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.338ex; width:1.088ex; height:1.676ex;" alt="{\displaystyle z}" loading="lazy"></span> entsprechen, und zwar den <i>Barkas-Andersen-Effekt</i> (proportional <span class="mwe-math-element mwe-math-element-inline"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle z^{3}}">
<semantics>
<mrow class="MJX-TeXAtom-ORD">
<mstyle displaystyle="true" scriptlevel="0">
<msup>
<mi>z</mi>
<mrow class="MJX-TeXAtom-ORD">
<mn>3</mn>
</mrow>
</msup>
</mstyle>
</mrow>
<annotation encoding="application/x-tex">{\displaystyle z^{3}}</annotation>
</semantics>
</math></span><img src="./_assets_/eb734a37dd21ce173a46342d1cc64c92/a8705461f87c505b475e26dee33ec60c04ef0aaa.svg" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.338ex; width:2.145ex; height:2.676ex;" alt="{\displaystyle z^{3}}" loading="lazy"></span> nach <a href="Walter_H._Barkas" title="Walter H. Barkas">Walter H. Barkas</a> und <a href="Hans_Henrik_Andersen" title="Hans Henrik Andersen">Hans Henrik Andersen</a>) und die Bloch-Korrektur (proportional <span class="mwe-math-element mwe-math-element-inline"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle z^{4}}">
<semantics>
<mrow class="MJX-TeXAtom-ORD">
<mstyle displaystyle="true" scriptlevel="0">
<msup>
<mi>z</mi>
<mrow class="MJX-TeXAtom-ORD">
<mn>4</mn>
</mrow>
</msup>
</mstyle>
</mrow>
<annotation encoding="application/x-tex">{\displaystyle z^{4}}</annotation>
</semantics>
</math></span><img src="./_assets_/eb734a37dd21ce173a46342d1cc64c92/3c096f1d742e750670cc824f543e4ea2e1741df9.svg" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.338ex; width:2.145ex; height:2.676ex;" alt="{\displaystyle z^{4}}" loading="lazy"></span>). Auch muss die Bewegung der Hüllenelektronen im Atom des Materials berücksichtigt werden („Schalenkorrektur“).
</p><p>Diese Korrekturen sind beispielsweise in den Programmen PSTAR und ASTAR des <a href="National_Institute_of_Standards_and_Technology" title="National Institute of Standards and Technology">National Institute of Standards and Technology</a> (NIST), die das Bremsvermögen für Protonen bzw. Alphateilchen berechnen, eingebaut.<sup id="cite_ref-11" class="reference"><a href="#cite_note-11"><span class="cite-bracket">[</span>11<span class="cite-bracket">]</span></a></sup> Die Korrekturen sind groß bei niedrigen Energien und werden immer kleiner, je größer die Energie wird.
</p><p>Zusätzlich kommt bei sehr hohen Energien noch <a href="Enrico_Fermi" title="Enrico Fermi">Fermis</a> Dichtekorrektur<sup id="cite_ref-ICRU49_10-2" class="reference"><a href="#cite_note-ICRU49-10"><span class="cite-bracket">[</span>10<span class="cite-bracket">]</span></a></sup> hinzu.
</p>
<div class="mw-heading mw-heading2"><h2 id="Literatur">Literatur</h2></div>
<ul><li>P. Sigmund: <i>Particle Penetration and Radiation Effects, General Aspects and Stopping of Swift Point Charges</i> (= <i>Springer Series in Solid State Sciences.</i> Vol. 151). Springer, Berlin/Heidelberg 2006, ISBN 978-3-540-72622-7.</li>
<li>H. Bethe: <cite style="font-style:italic">Zur Theorie des Durchgangs schneller Korpuskularstrahlen durch Materie</cite>. In: <cite style="font-style:italic">Annalen der Physik</cite>. <span style="white-space:nowrap">Band<span style="display:inline-block;width:.2em">&nbsp;</span>397</span>, <span style="white-space:nowrap">Nr.<span style="display:inline-block;width:.2em">&nbsp;</span>3</span>, 1930, <span style="white-space:nowrap">S.<span style="display:inline-block;width:.2em">&nbsp;</span>325–400</span>, <a href="Digital_Object_Identifier" title="Digital Object Identifier">doi</a>:<span class="uri-handle" style="white-space:nowrap"><a rel="nofollow" class="external text" href="https://doi.org/10.1002/andp.19303970303">10.1002/andp.19303970303</a></span> (Ursprüngliche Publikation von Bethe).<span class="Z3988" title="ctx_ver=Z39.88-2004&amp;rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&amp;rfr_id=info:sid/de.wikipedia.org:Bethe-Formel&amp;rft.atitle=Zur+Theorie+des+Durchgangs+schneller+Korpuskularstrahlen+durch+Materie&amp;rft.au=H.+Bethe&amp;rft.date=1930&amp;rft.doi=10.1002%2Fandp.19303970303&amp;rft.genre=journal&amp;rft.issue=3&amp;rft.jtitle=Annalen+der+Physik&amp;rft.pages=325-400&amp;rft.volume=397" style="display:none">&nbsp;</span></li>
<li>F. Bloch: <cite style="font-style:italic">Zur Bremsung rasch bewegter Teilchen beim Durchgang durch Materie</cite>. In: <cite style="font-style:italic">Annalen der Physik</cite>. <span style="white-space:nowrap">Band<span style="display:inline-block;width:.2em">&nbsp;</span>408</span>, <span style="white-space:nowrap">Nr.<span style="display:inline-block;width:.2em">&nbsp;</span>3</span>, 1933, <span style="white-space:nowrap">S.<span style="display:inline-block;width:.2em">&nbsp;</span>285–320</span>, <a href="Digital_Object_Identifier" title="Digital Object Identifier">doi</a>:<span class="uri-handle" style="white-space:nowrap"><a rel="nofollow" class="external text" href="https://doi.org/10.1002/andp.19334080303">10.1002/andp.19334080303</a></span> (Ursprüngliche Publikation von Bloch).<span class="Z3988" title="ctx_ver=Z39.88-2004&amp;rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&amp;rfr_id=info:sid/de.wikipedia.org:Bethe-Formel&amp;rft.atitle=Zur+Bremsung+rasch+bewegter+Teilchen+beim+Durchgang+durch+Materie&amp;rft.au=F.+Bloch&amp;rft.date=1933&amp;rft.doi=10.1002%2Fandp.19334080303&amp;rft.genre=journal&amp;rft.issue=3&amp;rft.jtitle=Annalen+der+Physik&amp;rft.pages=285-320&amp;rft.volume=408" style="display:none">&nbsp;</span></li>
<li>N. Bohr: <cite style="font-style:italic">On the theory of the decrease of velocity of moving electrified particles on passing through matter</cite>. In: <cite style="font-style:italic">The London, Edinburgh, and Dublin Philosophical Magazine and Journal of Science</cite>. <span style="white-space:nowrap">Band<span style="display:inline-block;width:.2em">&nbsp;</span>25</span>, <span style="white-space:nowrap">Nr.<span style="display:inline-block;width:.2em">&nbsp;</span>145</span>, 1913, <span style="white-space:nowrap">S.<span style="display:inline-block;width:.2em">&nbsp;</span>10–31</span>, <a href="Digital_Object_Identifier" title="Digital Object Identifier">doi</a>:<span class="uri-handle" style="white-space:nowrap"><a rel="nofollow" class="external text" href="https://doi.org/10.1080/14786440108634305">10.1080/14786440108634305</a></span> (Vorarbeiten von Bohr).<span class="Z3988" title="ctx_ver=Z39.88-2004&amp;rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&amp;rfr_id=info:sid/de.wikipedia.org:Bethe-Formel&amp;rft.atitle=On+the+theory+of+the+decrease+of+velocity+of+moving+electrified+particles+on+passing+through+matter&amp;rft.au=N.+Bohr&amp;rft.date=1913&amp;rft.doi=10.1080%2F14786440108634305&amp;rft.genre=journal&amp;rft.issue=145&amp;rft.jtitle=The+London%2C+Edinburgh%2C+and+Dublin+Philosophical+Magazine+and+Journal+of+Science&amp;rft.pages=10-31&amp;rft.volume=25" style="display:none">&nbsp;</span></li>
<li>N. Bohr: <cite style="font-style:italic">On the decrease of velocity of swiftly moving electrified particles in passing through matter</cite>. In: <cite style="font-style:italic">The London, Edinburgh, and Dublin Philosophical Magazine and Journal of Science</cite>. <span style="white-space:nowrap">Band<span style="display:inline-block;width:.2em">&nbsp;</span>30</span>, <span style="white-space:nowrap">Nr.<span style="display:inline-block;width:.2em">&nbsp;</span>178</span>, Oktober 1915, <span style="white-space:nowrap">S.<span style="display:inline-block;width:.2em">&nbsp;</span>581–612</span>, <a href="Digital_Object_Identifier" title="Digital Object Identifier">doi</a>:<span class="uri-handle" style="white-space:nowrap"><a rel="nofollow" class="external text" href="https://doi.org/10.1080/14786441008635432">10.1080/14786441008635432</a></span> (Vorarbeiten von Bohr).<span class="Z3988" title="ctx_ver=Z39.88-2004&amp;rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&amp;rfr_id=info:sid/de.wikipedia.org:Bethe-Formel&amp;rft.atitle=On+the+decrease+of+velocity+of+swiftly+moving+electrified+particles+in+passing+through+matter&amp;rft.au=N.+Bohr&amp;rft.date=1915-10&amp;rft.doi=10.1080%2F14786441008635432&amp;rft.genre=journal&amp;rft.issue=178&amp;rft.jtitle=The+London%2C+Edinburgh%2C+and+Dublin+Philosophical+Magazine+and+Journal+of+Science&amp;rft.pages=581-612&amp;rft.volume=30" style="display:none">&nbsp;</span></li></ul>
<div class="mw-heading mw-heading2"><h2 id="Weblinks">Weblinks</h2></div>
<ul><li><a rel="nofollow" class="external text" href="https://pdg.lbl.gov/2006/reviews/passagerpp.pdf">Durchgang geladener Teilchen durch Materie, inklusive Plot</a> (engl.; PDF-Datei; 512&nbsp;kB)</li>
<li><a rel="nofollow" class="external text" href="https://www.physics.nist.gov/PhysRefData/Star/Text/programs.html">Bremsvermögen für Protonen und Alphateilchen</a> (engl.)</li>
<li><a rel="nofollow" class="external text" href="https://www-nds.iaea.org/stopping/">Stopping Power Daten und Kurven</a> (engl.)</li></ul>
<div class="mw-heading mw-heading2"><h2 id="Einzelnachweise">Einzelnachweise</h2></div>
<ol class="references">
<li id="cite_note-1"><span class="mw-cite-backlink"><a href="#cite_ref-1">↑</a></span> <span class="reference-text">N. Bohr: <cite style="font-style:italic">On the theory of the decrease of velocity of moving electrified particles on passing through matter</cite>. In: <cite style="font-style:italic">The London, Edinburgh, and Dublin Philosophical Magazine and Journal of Science</cite>. <span style="white-space:nowrap">Band<span style="display:inline-block;width:.2em">&nbsp;</span>25</span>, <span style="white-space:nowrap">Nr.<span style="display:inline-block;width:.2em">&nbsp;</span>145</span>, 1913, <span style="white-space:nowrap">S.<span style="display:inline-block;width:.2em">&nbsp;</span>10–31</span>, <a href="Digital_Object_Identifier" title="Digital Object Identifier">doi</a>:<span class="uri-handle" style="white-space:nowrap"><a rel="nofollow" class="external text" href="https://doi.org/10.1080/14786440108634305">10.1080/14786440108634305</a></span>.<span class="Z3988" title="ctx_ver=Z39.88-2004&amp;rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&amp;rfr_id=info:sid/de.wikipedia.org:Bethe-Formel&amp;rft.atitle=On+the+theory+of+the+decrease+of+velocity+of+moving+electrified+particles+on+passing+through+matter&amp;rft.au=N.+Bohr&amp;rft.date=1913&amp;rft.doi=10.1080%2F14786440108634305&amp;rft.genre=journal&amp;rft.issue=145&amp;rft.jtitle=The+London%2C+Edinburgh%2C+and+Dublin+Philosophical+Magazine+and+Journal+of+Science&amp;rft.pages=10-31&amp;rft.volume=25" style="display:none">&nbsp;</span></span>
</li>
<li id="cite_note-2"><span class="mw-cite-backlink"><a href="#cite_ref-2">↑</a></span> <span class="reference-text">P. Sigmund: <i>Particle Penetration and Radiation Effects, General Aspects and Stopping of Swift Point Charges</i> (= <i>Springer Series in Solid State Sciences.</i> Vol. 151). Springer, Berlin/Heidelberg 2006, ISBN 978-3-540-72622-7.</span>
</li>
<li id="cite_note-3"><span class="mw-cite-backlink"><a href="#cite_ref-3">↑</a></span> <span class="reference-text">H. A. Bethe, J. Ashkin: <cite style="font-style:italic">Passage of radiation through matter</cite>. In: E. Segré (Hrsg.): <cite style="font-style:italic">Experimental Nuclear Physics</cite>. Vol. 1, Part II. New York 1953, <span style="white-space:nowrap">S.<span style="display:inline-block;width:.2em">&nbsp;</span>253</span>.<span class="Z3988" title="ctx_ver=Z39.88-2004&amp;rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&amp;rfr_id=info:sid/de.wikipedia.org:Bethe-Formel&amp;rft.atitle=Passage+of+radiation+through+matter&amp;rft.au=H.+A.+Bethe%2C+J.+Ashkin&amp;rft.btitle=Experimental+Nuclear+Physics&amp;rft.date=1953&amp;rft.genre=book&amp;rft.pages=253&amp;rft.place=New+York&amp;rft.volume=Vol.+1%2C+Part+II" style="display:none">&nbsp;</span></span>
</li>
<li id="cite_note-4"><span class="mw-cite-backlink"><a href="#cite_ref-4">↑</a></span> <span class="reference-text">cern.ch: <style data-mw-deduplicate="TemplateStyles:r261891140">
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</style><a rel="nofollow" class="external text" href="https://web.archive.org/web/20131214003024/http://geant4.web.cern.ch/geant4/G4UsersDocuments/UsersGuides/PhysicsReferenceManual/html/node41.html">Ionization</a> (<span class="webarchiv-memento"><a href="Webarchivierung#Begrifflichkeiten" title="Webarchivierung">Memento</a></span> vom 14. Dezember 2013 im <i><a href="Internet_Archive" title="Internet Archive">Internet Archive</a></i>)</span>
</li>
<li id="cite_note-5"><span class="mw-cite-backlink"><a href="#cite_ref-5">↑</a></span> <span class="reference-text"><a rel="nofollow" class="external text" href="https://web.archive.org/web/20120206072234/http://www.exphys.uni-linz.ac.at/Stopping/">Bildquelle</a> (<span class="webarchiv-memento"><a href="Webarchivierung#Begrifflichkeiten" title="Webarchivierung">Memento</a></span> vom 6. Februar 2012 im <i><a href="Internet_Archive" title="Internet Archive">Internet Archive</a></i>)</span>
</li>
<li id="cite_note-6"><span class="mw-cite-backlink"><a href="#cite_ref-6">↑</a></span> <span class="reference-text">K. Bethge, G. Walter, B. Wiedemann: <i>Kernphysik</i>. 3. Auflage, Springer, 2007, S. 118, 121.</span>
</li>
<li id="cite_note-7"><span class="mw-cite-backlink"><a href="#cite_ref-7">↑</a></span> <span class="reference-text"><a href="J%C3%BCrgen_Kiefer_(Biophysiker)" title="Jürgen Kiefer (Biophysiker)">Jürgen Kiefer</a>: <i>Biologische Strahlenwirkung. Eine Einführung in die Grundlagen von Strahlenschutz und Strahlenanwendung.</i> Heidelberg (Springer) 1981, ISBN 978-3-642-67947-6, S. 47</span>
</li>
<li id="cite_note-8"><span class="mw-cite-backlink"><a href="#cite_ref-8">↑</a></span> <span class="reference-text"><a href="Claude_Amsler" title="Claude Amsler">Claude Amsler</a>: <cite style="font-style:italic">Kern- und Teilchenphysik</cite>. vdf Hochschulverlag AG, 2007, ISBN 978-3-8252-2885-9, <span style="white-space:nowrap">S.<span style="display:inline-block;width:.2em">&nbsp;</span>116</span> (<a rel="nofollow" class="external text" href="https://books.google.de/books?id=eKGVz67GLp0C&amp;pg=PA116#v=onepage">eingeschränkte Vorschau</a> in der Google-Buchsuche).<span class="Z3988" title="ctx_ver=Z39.88-2004&amp;rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&amp;rfr_id=info:sid/de.wikipedia.org:Bethe-Formel&amp;rft.au=Claude+Amsler&amp;rft.btitle=Kern-+und+Teilchenphysik&amp;rft.date=2007&amp;rft.genre=book&amp;rft.isbn=9783825228859&amp;rft.pages=116&amp;rft.pub=vdf+Hochschulverlag+AG" style="display:none">&nbsp;</span></span>
</li>
<li id="cite_note-9"><span class="mw-cite-backlink"><a href="#cite_ref-9">↑</a></span> <span class="reference-text">F. Bloch: <cite style="font-style:italic">Zur Bremsung rasch bewegter Teilchen beim Durchgang durch Materie</cite>. In: <cite style="font-style:italic">Annalen der Physik</cite>. <span style="white-space:nowrap">Band<span style="display:inline-block;width:.2em">&nbsp;</span>408</span>, <span style="white-space:nowrap">Nr.<span style="display:inline-block;width:.2em">&nbsp;</span>3</span>, 1933, <span style="white-space:nowrap">S.<span style="display:inline-block;width:.2em">&nbsp;</span>285–320</span>, <a href="Digital_Object_Identifier" title="Digital Object Identifier">doi</a>:<span class="uri-handle" style="white-space:nowrap"><a rel="nofollow" class="external text" href="https://doi.org/10.1002/andp.19334080303">10.1002/andp.19334080303</a></span>.<span class="Z3988" title="ctx_ver=Z39.88-2004&amp;rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&amp;rfr_id=info:sid/de.wikipedia.org:Bethe-Formel&amp;rft.atitle=Zur+Bremsung+rasch+bewegter+Teilchen+beim+Durchgang+durch+Materie&amp;rft.au=F.+Bloch&amp;rft.date=1933&amp;rft.doi=10.1002%2Fandp.19334080303&amp;rft.genre=journal&amp;rft.issue=3&amp;rft.jtitle=Annalen+der+Physik&amp;rft.pages=285-320&amp;rft.volume=408" style="display:none">&nbsp;</span></span>
</li>
<li id="cite_note-ICRU49-10"><span class="mw-cite-backlink">↑ <sup><a href="#cite_ref-ICRU49_10-0">a</a></sup> <sup><a href="#cite_ref-ICRU49_10-1">b</a></sup> <sup><a href="#cite_ref-ICRU49_10-2">c</a></sup></span> <span class="reference-text">ICRU Report 49, <i>Stopping Powers and Ranges for Protons and Alpha Particles</i>. International Commission on Radiation Units and Measurements, Bethesda, MD, USA (1993)</span>
</li>
<li id="cite_note-11"><span class="mw-cite-backlink"><a href="#cite_ref-11">↑</a></span> <span class="reference-text"><a rel="nofollow" class="external text" href="https://www.physics.nist.gov/PhysRefData/Star/Text/programs.html">PSTAR and ASTAR Databases for Protons and Helium Ions</a></span>
</li>
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