Tunnelling decay constant
= Tunnelling decay constant
{title2=$\kappa=\sqrt{2m(V_0-E)}/\hbar$}
The <tunnelling decay constant> is the inverse length controlling the <exponential decay> of an <evanescent wave> in a constant <potential barrier> with $E<V_0$. The <wavefunction> amplitude decay length is $1/\kappa$; the squared-amplitude decay length is $1/(2\kappa)$.