THE USE OF THE OXYGEN AUGER PARAMETERS IN THE CHARACTERIZATION OF OXYGEN-CONTAINING-COMPOUNDS

Electronic relaxation phenomena play a key role in determining the chemical shift observed in photoemission and Auger transitions. The aim of this paper is to investigate the relaxation effects in oxygen-containing compounds by means of two oxygen Auger parameters alpha' = E(B)(1s) +E(K)(KL23L23; 1D) and beta' = E(B)(1s) + E(K)(KL1L23; 1P). It is shown that shifts of these Auger parameters with respect to the water molecule in the gas phase can be related directly to the hole-hole repulsion energies U(2p2p) and U(2s2p), and they therefore contain very useful information on the nature of the chemical bonds involving oxygen. The hole-hole repulsion energy values are reduced with respect to the atomic or free ion values by screening and polarisation in the molecular or solid state. U(2p2p) values for high-T(c) copper oxide superconductors are also of interest because these quantities are necessary to calculate the ex-change and superexchange interactions between the O2p hole and the Cu3d9 spin, which are crucial to our understanding of the physics of these materials. Considering a large data set of oxygen-containing compounds we show that, (1) U(2p2p) (eV) almost-equal-to 8.5 - DELTA-alpha' and U(2s2p) (eV) almost-equal-to 16.5 - DELTA-beta' where the Auger parameter shifts are calculated with respect to H2O (g) with alpha' (H2O(g)) = 1038.5 eV and beta' (H2O(g)) = 1014.5 eV, (2) DELTA-alpha' and DELTA-beta' are roughly linearly correlated, the slope being distinctive of compounds with similar chemical character (metal-oxygen or non-metal-oxygen bonds), (3) larger values of the Auger parameter shifts are obtained for compounds where the nearest-neighbour metal ions have high polarisability, as in the case of transition metal oxides and oxyanions.