L2 DISCRETIZATION OF ATOMIC AND MOLECULAR ELECTRONIC CONTINUA - MOMENT, QUADRATURE AND J-MATRIX TECHNIQUES

A review of the process of extraction of continuum information from operators discretized in finite sets of square integrable (L2) basis functions is given, with emphasis on the close relationships between the Stieltjes method and Gaussian integration. Examples of recent applications are given in the areas of atomic and molecular photoabsorption (He, Ne*, H2, Ar*2), Stieltjes determination of e- -atom/molecule resonances (He, He-, Mg-, N-2) and e+ -H scattering at intermediate energies. Finally, photoabsorption of H- leading to H+ + 2e- is discussed using the J-matrix technique, which involves an infinite L2 expansion, and combines advantages of the finite L2 methods with those of the traditional close coupling method. © 1979.