Isotopic oxygen exchange

160/180 isotopic exchange has been studied over several metal oxides and supported metal catalysts.According to Boreskov, Winter, and Novakova there are three types of oxygen exchange  

Homoexchange experiments use an equimolar mixture of Og(g) and 02(g) and monitor the formation of 0 0(g), Eq. (3.14), with time in order to study the oxygen activation on the solid surface. - - On the other hand, in the heteroexchange experiments, a mixture of 02(g) in He or Ar is passed over a solid pre-oxidized with 02(g), and the production of 0 0 and 02 gases is monitored as a function of time (THE) or temperature (TPIE). These experiments can be used to study surface and bulk 

At reaction temperatures higher than 400 °C, two more steps might be involved  

Information about the exchange mechanism can be obtained from the relative evolution of the oxygen isotopomer concentrations 

Similarly, peroxide species 0 could be the result of the reaction of molecular oxygen with two neighboring reduced cerium centers, where two electrons are transferred from the solid to the molecular oxygen  

Scanning electron microscopy shows that A1 diffuses into the bulk during oxidation [585]. 

Low-energy electron diffraction shows the formation of a c(2 x4) structure on Fe(llO) [54]. There is no evidence for the formation of K-oxide at K-coverages less than one monolayer [554]. The bulk oxidation starts approximately at Fe O = 1 0.5 independent of K coverage [554]. N and O interacts with K [515]. 

The 0(ls) X-ray photoelectron spectroscopy peak at 530.0 eV is independent of K coverage and of O-coverage [554]. At small coverages by O the work function is decreased for O/K/Fe due to depolarization of K-K interactions [500]. 

Preadsorbed N does not inhibit O2 chemisorption [415] since the preadsorbed N is displaced to the bulk Fe upon O2 exposure at 300 K [477, 486]. The presence of N in the bulk decreases the tendency for oxidation of the Fe [477]. The N dissolved in the bulk can only be removed by desorption after the O layer has been removed by reduction [477]. 

At 77 K H2O is chemisorbed without dissociation [586, 587]. The chemisorption energy of H2O is 54.6-66 kJ/mole [586, 587]. Sputtering of the surface does not destroy the passivating effect of the adsorbed H2O [588], while the electron beam during a Auger electron spectroscopy experiment leads to oxidation and destruction of the passivation [588]. 

---

V.A. Sobyanin, V.I. Sobolev, V.D. Belyaev, O.A. Mar ina, A.K. Demin, and A.S. Lipilin, On the origin of the Non-Faradaic electrochemical modification of catalytic activity (NEMCA) phenomena. Oxygen isotope exchange on Pt electrode in cell with solid oxide electrolyte, Catal. Lett. 18, 153-164 (1993). 

Figure 1.29. Calculated changes in the S 0 values of volcanic rocks (5 0 = +7.0%c) as a result of equilibrium oxygen isotope exchange with waters of different initial compositions. The dotted areas represent the ranges of rocks in the zeolite and the sericite-chlorite zones (Green et al., 1983).

Iengo E, Scandola F, Alessio E (2006) Metal-Mediated Multi-Porphyrin Discrete Assemblies and Their Photoinduced Properties 121 105-143 Itoh M, Taniguchi H (2007) Ferroelectricity of SrTiC>3 Induced by Oxygen Isotope Exchange. 124 89-118... 

Oxyacids of sulphur and their anhydrides, mechanisms and reactivity in reactions of organic, 17, 65 Oxygen isotope exchange reactions of organic compounds, 3, 123... 

Oxygen isotope exchange reactions of organic compounds, 3, 123... 

Criss, R. E., Gregory, R. T. Taylor, H. P., Jr (1987). Kinetic theory of oxygen isotopic exchange between minerals and water. Geochim. Cosmochim. Acta, 51, 1099-108. 

Criss RE (1999) Principles of Stable Isotope Distribution. Oxford Univ Press, New York Criss RE, Gregory RT, Taylor HP (1987) Kinetic theory of oxygen isotope exchange between minerals and water. Geochim Cosmochim Acta 51 1099-1108... 

Bottinga Y (1968) Calculations of fractionation factors for carbon and oxygen isotope exchange in the system calcite-carbon dioxide-water. J Phys Chem 72 800-808 Bullen TD, White AF, Childs CW, Vivit DV, Schulz MS (2001) Demonstration of significant abiotic iron isotope fractionation in nature. Geology 29 699-702... 

Yund R. A. and Anderson T. F. (1974). Oxygen isotope exchange between potassium feldspar and KCl solution. In Geochemical Transport and Kinetics, Hofmann, Giletti, Yoder, and Yund, eds. New York Carnegie Inst. Washington and Academic Press. 

Gregory, R.T., et al. 1989. Oxygen isotope exchange kinetics of mineral pairs in closed and open systems application to problems of hydrothermal alteration of igneous rocks and Precambrian iron formations. Chemical Geology, 75, 1-42. 

Detailed studies of the kinetics and mechanisms of oxygen isotope exchange between minerals and fluids show that there are three possible exchange mechanisms (Matthews et al. 1983b, c Giletti 1985). 

Criss et al. (1987) and Gregory et al. (1989) developed a theoretical framework that describes the kinetics of oxygen isotope exchange between minerals and coexisting fluids. Figure 2.17 shows characteristic patterns in 8-5 plots for some hy-drothermally altered granitic and gabbroic rocks. The arrays displayed on... 

Fig. 2.17 cut across the 45° equilibrium lines at a steep angle as a result of the much faster oxygen isotope exchange of feldspar compared to that of quartz and pyroxene. If a low- 0 fluid such as meteoric or ocean water is involved in the exchange process, the slopes of the disequilibrium arrays can be regarded as isochrons where, with continued exchange through time the slopes become less steep and approach the 45° equilibrium line. These times represent the duration of a particular hydrothermal event. 

Fritz P, Basharmel GM, Drimmie RJ, Ibsen J, Qureshi RM (1989) Oxygen isotope exchange between sulphate and water during bacterial reduction of sulphate. Chem Geol 79 99-105 Fry B (1988) Food web structure on Georges Bank from stable C, N and S isotopic compositions. Limnol Oceanogr 3 1182-1190... 

Paytan A, Luz B, Kolodny Y, Neori A (2002) Biologically mediated oxygen isotope exchange between water and phosphorus. Global Biogeochem Cycles 16-13 1-7 Paytan A, Kastner M, Campbell D, Thiemens M (2004) Seawater sulfur isotope fluctuations in the Cretaceous, Science 304 1663-1665... 

Usdowski E, Hoefs J (1993) Oxygen isotope exchange between carbonic acid, bicarbonate, carbonate, and water a re-examination of the data of McCrea and an expression for the overall partitioning of oxygen isotopes between the carbonate species and water. Geochim Cosmochim Acta 57 3815-3818... 

Esters can be hydrolyzed nonenzymatically in acidic and alkahne solutions. In both cases, a tetrahedral intermediate is indicated on the basis of the measured rates of hydrolysis and the rates of oxygen isotope exchange. 

ATOM PERCENT EXCESS OXYGEN ISOTOPE EXCHANGE COMPARTMENTAL ANALYSIS ISOTOPE EXCHANGE KINETICS GRAPHICAL METHODS... 

Ferroelectricity of SrTiOs Induced by Oxygen Isotope Exchange... 

Keywords SrTiOs Oxygen isotope exchange Quantum paraelectricity ... 

---