Nitrogen oxide clusters atomic oxygen

The exceptional activity exhibited by ion-exchanged copper ZSM-5 zeolite catalysts for nitric oxide (NO) decomposition, and for the selective catalytic reduction (SCR) of nitrogen oxides (NOx) in the presence of excess oxygen is well documented [1-10]. The nature of the active copper species in the SCR reaction however still remains uncertain. We and others have recognised that there are two different types of copper species within the ZSM-5 zeolite channels [11]. Isolated copper ions exist in low symmetry environments, and small clusters, where the copper atoms are linked by extra-lattice oxygen species such as [Cu(II)-0-Cu(n)] dimers, are also present. Recent studies have also suggested that the isolated copper ions in ZSM-5 occupy two types of sites [11], which may have different SCR reactivity. It is likely... 

The achievable ablation rates depend on the sample composition, the discharge gas and its pressure. As a filler gas a noble gas is normally used. Indeed, in the case of nitrogen or oxygen, chemical reactions at the sample surface would occur and disturb the sputtering, as electrically non-conductive oxide or nitride layers would be formed. Furthermore, reactions with the ablated material would produce molecular species, which emit molecular band spectra in optical atomic spectrometry or produce cluster ion signals in mass spectrometry. In both cases severe spectral in-... 

The enzyme contains two nickel-centered fragments the first one is a cluster containing Fe and Ni, whereas the second one, remote from the first one, is supposed to be responsible for CO oxidation. EXAFS shows that the Ni atoms of both sites have a nitrogen, oxygen and sulfur environment. Complexes based on nickel that serve as models for this enzyme have been synthesized by the groups of Crabtree in Yale and Holm in Harvard. 

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