Theoretical study of processes of multiple excitation/ionization in K-photoabsorption of carbon and nitrogen in CO and N-2 molecules

Spectra of multiple excitation/ionization in the region of photoabsorption K-edge of carbon and nitrogen of CO and N-2 molecules in the gas phase are studied theoretically. Processes of additional excitation/ionization from t he 1 pi and 5 sigma shells are taken into account. Single-electron wave fun ctions in the excited state are calculated allowing for the effect of core wave functions in the field of a vacancy by the single-center method in the Hartree-Fock approximation. Cross sections for photoabsorption are calcula ted using the theory of nonorthogonal orbitals. The influence of many-elect ron correlations on the extension of the multiplet structure of certain con figurations of multiple excitation is studied. (C) 2000 MAIK "Nauka/Interpe riodica".