A quantum particle of mass m is moving in a one dimensional potential
\(V(x)=V_0 θ(x)-λ δ(x)\),
where V0 and λ are positive constants, θ(x) is the Heaviside step function and δ(x) is the Dirac delta function. The leading contribution to the reflection coefficient for the particle incident from the left with energy E >> V0 > λ and \(\sqrt{2 m E} \gg \frac{V_0 h}{\lambda}\) is
1
\(\frac{V_0^2}{4 E^2}\)
2
\(\frac{V_0^2}{8 E^2}\)
3
\(\frac{m \lambda^2}{2 E h^2}\)
4
\(\frac{m \lambda^2}{4 E h^2}\)