# Single barrier with impurity as a 1D resonant tunneling model

Friends,
I am trying to consider an impurity which can be viewed as a 1D resonant-tunnelling problem.
I gather that the transmission coefficients TL and TR will decay exponentially from the impurity to the edges of the barrier. However, I am unsure how to predict how the peak & area of T(E) depend on the location of the impurity in the barrier...Davies on p.203, 5.16 reveals that the resonant tunneling is most effective when the impurity is placed in the center, but I am unsure why.
Thanks for any help.
M.Bungle