Theoretical studies of core excitation and ionization in molecular systems

Photoionization cross sections have been computed using correlated initial and final target states obtained with standard ab initio techniques and usi ng a numerical representation of the continuum scattering orbitals. Here, c ore ionization of small molecular systems will be focused on. A brief revie w of previous results obtained using these methods is given. New results ar e then given for the N 1s ionization of NO and the N 1s ionization of N-2. In the study of NO, the spin-coupling scheme which best describes the shape -resonant state and the energy dependence of the branching ratios for the s inglet and triplet final ion states will be considered. In the study of N-2 core ionization, the effects of the coupling of nearly degenerate core lev els and the effects of correlation on the importance of interchannel coupli ng will be considered.