Orthogonalized-plane-wave approximation in the calculation of photoionization cross sections of molecules

The physical bases of the OPW approximation in the calculation of molecular photoionization cross sections are considered in terms of the scattering theory, and the ways of improving the calculations within the framework of OPW approximation are discussed. Numerical calculations are done on several molecules by the oridinary OPW method and by its modification using the bound orbitals obtained by ab initio SCF-MO calculations with gaussian basis set. (Auth.)