The Iterative Schwinger Variational Method Applied to Electron-Molecule Continuum Processes
<p>We have developed the iterative Schwinger variational method to study electron-molecule scattering problems within the Hartree-Fock approximation. The method is based on the iterative use of the Schwinger variational principle and can obtain exact static-exchange scattering solutions. This...
| Summary: | <p>We have developed the iterative Schwinger variational method to study electron-molecule scattering problems within the Hartree-Fock approximation. The method is based on the iterative use of the Schwinger variational principle and can obtain exact static-exchange scattering solutions. This approach has been implemented using standard single-center expansion techniques. We present results using the Schwinger variational expression for e-He and e-He<sup>+</sup> collisions and find very rapid convergence of the phase shifts with increasing basis set size. We then discuss the iterative use of the Schwinger variational expression and give results for e-H<sub>2</sub> and e-H<sup>+</sup><sub>2</sub> scattering which show very rapid convergence of the iterative method. We have applied this method to low energy 3-CO<sub>2</sub> scattering and obtained differential and integral elastic scattering cross sections. We determined that the <sup>2</sup>π<sub>u</sub> shape resonance in this system occurs at an energy of 5.39 eV with a width of 0.64 eV in contrast to previously published static-exchange results.</p>
<p>We have also used the iterative Schwinger variational method to study the valence shell photoionization of N<sub>2</sub> and CO<sub>2</sub> as well as the K-shell photoionization of CO<sub>2</sub>. These results agree well with available experimental data. The vibrational branching ratios for photoionization of 3σ<sub>g</sub> level of N<sub>2</sub> were found to agree quantitatively with experimental measurements when an adequate number of internuclear spacings were considered. The effects of vibrational averaging on 4σ<sub>g</sub> photoionization of CO<sub>2</sub> were also studied. A detailed comparison of the results obtained using the Schwinger method and other theoretical methods for studying photoionization has been made.</p>
<p>The iterative Schwinger variational method has proven to be an accurate and efficient method for obtaining Hartree-Fock level scattering solutions, and it has allowed us to study electron-molecule continuum processes in more detail and for larger systems than previously possible.</p> |
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