Search

In order to understand the physics of radiation-induced proton density decay in thin SiO/sub 2/ films, we performed ab initio Hartree-Fock calculations of the potential energy curves for the interaction between model oxide clusters and H in two charge states. The calculated results led to two separate proposed mechanisms for proton density decay in thin SiO/sub 2/ films: (1) electronic excitation involving hot phonon levels of the ground electronic state at low photon-energy radiation and (2) electron capture by protons at high photon-energy radiation. The proposed mechanisms qualitatively explain recent experimental observations.

Fast atom bombardment (FAB) mass spectrometry of the gold(I) and gold(III) derivatives, {Au[C(Y)–NHAr]2}+X− and {Au[C(Y)–NHAr]2I2} + X− (Y =OC2H5 or NHAr; X− = CIO4− or BF4−; Ar = p-CH3C6H4) has led to the detection, for the alkoxyamino derivatives only, of [M–H]+˙ molecular species. The mechanism of the formation of these unusual species has been studied with respect to the oxidation state of gold, nature of the matrix, matrix acidity and ligand structure. The energetics of two possible alternative mechanisms has been studied by means of ab initio theoretical calculations. Both experimental and theoretical data indicate that [M–H]+˙ formation is due to the reaction of M+ with H+-philic and/or H˙-philic species produced from the matrix by FAB. Whatever the operative mechanism, the [M–H]+˙ formation is to be considered a FAB-induced oxidative process.

Ab initio cluster model calculations on the interaction of CO and CO2 with NiO and MgO surface and defect sites are reviewed. NiO behaves very similarly as the non-transition metal oxide MgO towards CO chemisorption because the bonding of CO to these surfaces is dominated by electrostatic terms and involves a very modest σ donation or, in the NiO case, π back donation. The role of the surface defects in determining the reactivity of oxides toward CO and CO2 chemisorption is shown.