= Mass dependence of fixed-barrier tunnelling
{title2=$-\log T\sim\sqrt m$}
At fixed incident <energy> and fixed potential-energy profile, the forbidden-region WKB action is $\int\sqrt{2m(V-E)}\,dx$. Its leading transmission exponent grows as the square root of <mass>. Equal electrostatic voltages need not define equal potential-energy barriers for particles with different charges. The leading exponential comparison assumes a sufficiently opaque barrier; prefactors and the WKB turning-point conditions remain relevant.
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