Calculation of the photoionization cross section of N₂from first threshold at 500 AA

A method of determining photoionization cross sections for homonuclear diatomic molecules is outlined. For the initial electronic states self-consistent field-linear combination of atomic orbitals-molecular orbital wave functions constructed from Slater type atomic orbitals are used. A preliminary calculation is performed using two-centre Coulomb waves for the final electronic states. The quantum-defect approach to finding phase shifts is investigated but uncertainties in the interpretations of Rydberg series of molecular states makes it difficult to obtain reliable continuum functions. Results are given for photoionizing transitions in N 2 (x 1 Sigma g + ) which give rise to the states N 2 + (x 2 Sigma g + , A 2 Pi u , B 2 Sigma u + ). The vibrational states are accounted for with Franck-Condon factors.