Variational Approach to Perturbation Theory. II. An Extension of the Minimum Principle

摘要

The variational principle used to calculate the interaction of an atom or molecule with a weak electrohyphen;magnetic field is cast in a form analogous to the Kato identity of atomic scattering theory. A theorem from the literature of scattering theory is then used to extend the conditions under which the variational approach to perturbation theory becomes a true minimum.