<a href="https://en.wikipedia.org/wiki/Boltzmann_factor" class="extiw" title="en:Boltzmann factor">Boltzmann factor</a> decreases exponentially with the state energy.
<a href="https://meta.wikimedia.org/wiki/user:egg" class="extiw" title="meta:user:egg">Vojtěch Hála</a>
own work (KmPlot, Inkscape)