We present here a new approach to nonrelativistic perturbation theory. We show that in problems reducible to one dimension, the energy shifts and wave-function corrections, including corrections to the position of the nodes, to any order, can be expressed in quadrature in a hierarchy scheme. The second-order energy shift calculated is explicitly shown to be equivalent to that in the ordinary Rayleigh-Schrödinger theory.

• Received 26 February 1979

DOI:https://doi.org/10.1103/PhysRevLett.42.1582