Some theorems on perturbation theory. Ill

Abstract

The behaviour of the spectrum of the differential equation d 2 ɸ / dx 2 + { λ - q ( x ) - ϵσ ( x )} ɸ = 0 is considered in the case where the unperturbed spectrum is discrete and the perturbed spectrum is continuous. An example is given to show what meaning can be attached to the classical perturbation formula in this case.