Semiclassical perturbation approach to quantum reflection

We consider the problem of quantum ``reflection above the barrier,'' introducing a distorted-wave Born approximation based on the primitive semiclassical Wentzel-Kramers-Brillouin wave function. The idea generalizes to the concept of an unperturbed Hamiltonian defined as the exact Hamiltonian plus small parts which ``turn off'' nonclassical processes such as barrier reflection and barrier tunneling. {} 1996 The American Physical Society.