CALCULATION OF 2-CENTER INTEGRALS INVOLVING A RAPIDLY OSCILLATING FREE-ELECTRON WAVE-FUNCTION

Optical potentials are used in a quantum mechanical treatment of loss processes, e.g., ionization, where the loss of flux is described by th e imaginary part. We present a numerical method for calculating two-ce nter two-electron intervals necessary to construct the imaginary part of the optical potential. By introducing Slater-type orbitals with com plex-valued exponents (CSTOs), wt are able to represent the free elect ron wave with a Limited number of CSTOs. For the representation of fre e electron wave functions with many oscillations, i.e., in a large r r ange or far a high kinetic energy, these new CSTOs form a more natural set of basis functions. The introduction of CSTOs is inevitable for t he calculation of integrals concerning collisions in the mK energy ran ge, where the interaction acts over large internuclear distances. Exte nsive numerical checks show that the final imaginary part of the optic al potentials can be calculated with an accuracy better than 2%. (C) 1 997 American Institute of Physics.