Application of a new variational functional for electron-molecule collisions: an extension of the Schwinger variational principle

A variational functional for scattering theory is discussed which has been recently proposed by Takatsuka and McKoy (Phys. Rev.; A23:2352 (1981)). It is shown that this functional can provide results with a purely discrete set of functions which are approximately equivalent to those obtained by Lucchese et al (Phys. Rev.; A21:112 (1980)) from the first iteration of the iterative Schwinger method. Applications to the scattering of electrons by systems including CO+ and LiH illustrate this relationship and other features of the method. (author)