a Zero Core-Contribution Model for Photodetachment of Atomic and Molecular Negative Ions.

In this thesis a simple model for computing photodetachment cross sections is developed. The model represents a negative ion by an equivalent one electron system. It is simple to apply since only the asymptotic behavior of the electron's wave function is required. For atomic negative ions, only the orbital angular momentum, , of an electron in the outermost shell, the electron affinity and the atomic radius of the parent neutral atom need be known. Comparable information is required for molecular ions. This information is available for many ions from sources independent of photodetachment experiments. The model shows that atomic ions divide into groups according to their value of . Within each group, ions have cross sections sharing common features, with the maximum cross sections being nearly proportional to the square of the atomic radii of the parent atoms. The model is applied to the homonuclear diatomic ions O(,2) and S(,2). In addition to computing the total photodetment cross section, the model gives information about detachment associated with single vibrational transitions. The results of the model are in good agreement with experiment. To our knowledge, this is the first computation of photodetachment cross sections of these molecular negative ions which includes vibrational effects.