Many-electron and orientation effects in anomalous elastic scattering of an x-ray photon by a linear molecule

A strong orientation effect is discovered theoretically upon the change of the scheme of a suggested experiment on the anomalous elastic x-ray scatter ing of linearly polarized x-ray radiation by linear diatomics near the ioni zation thresholds of inner molecular orbitals. The effects on the shape of theoretical scattering spectra of vibronic phenomena (for the HF and HCl mo lecules) are studied, as well as the additional excitation/ionization of ou ter-shell electrons (the CO molecule). Within the one-centre approximation for the molecular orbital wavefunctions the analytical structure of the lin ear molecule's form factor is obtained. The calculation of one-electron wav efunctions is carried out with the inclusion of the effect of core relaxati on in the field of the inner-shell vacancy within the one-centre method in the Hartree-Fock approximation. The dipole transition matrix elements and p hotoabsorption cross sections are calculated by the methods of the theory o f non-orthogonal orbitals.