The properties of off-shell coulomb radial wavefunctions.

Approximations to exact wave functions for the scattering of few-particle systems often involve components corresponding to the interaction of two of the particles 'off the energy-shell'. Several examples arising in the collision of ions and photons with atoms are given. An expansion in partial waves leads to an off-shell radial wave function. The defining differential equation is solved here numerically with particular emphasis on the behaviour arising from two-body potentials of long-range Coulomb form. The transition to shell of the radial wave functions, Jost functions and solutions and T-matrix elements is discussed for both short-range and Coulomb potentials. It is shown that the approximation of a Coulomb potential by a shorter-range form involves little error when sufficiently far off the energy shell. [ABSTRACT FROM AUTHOR]