NITROGEN K-SHELL EXCITATIONS IN COMPLEX-MOLECULES AND POLYPYRROLE

Experimental and theoretical studies of nitrogen K-shell near-edge abs orption in complex compounds such as thiourea, benzalaniline, pyrrole, polypyrrole, tetraethylammonium, tetrabutylammonium and substituted 2 -hydroxy-3-methoxy-benzylidene-aniline compounds were carried out. The quasi-atomic model was used in order to calculate the spectral distri bution of oscillator strengths for transitions from the N1s level to e xcited discrete and continuum states, to explain general trends in the changes of K-shell excitation spectra and to reveal their relationshi ps with chemical bonding of the N atom in the compounds. The performed analysis of theoretical and experimental spectra evidences the centra l role of splitting of an intense N1s(-1)2p resonance in NK XANES form ation in all compounds under study. The influence of the electronic ch arge transfer, bond conjugation and localization on the energies and i ntensities of pi and sigma* resonances are discussed in detail. The s trong connection between interference and chemical bonding effects on the main resonance features of X-ray absorption in the compounds under study is revealed.