One particle exchange <a href="https://en.wikipedia.org/wiki/Feynman_diagram" class="extiw" title="w:Feynman diagram">Feynman diagram</a>.
<a href="//commons.wikimedia.org/wiki/User:Stannered" title="User:Stannered">User:Stannered</a>
2007-03-07
<a href="https://en.wikipedia.org/wiki/Image:1pxchg.png" class="extiw" title="en:Image:1pxchg.png">en:Image:1pxchg.png</a>