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Reactivity of atomic gold anions toward oxygen and the oxidation of CO: experiment and theory 总被引:1,自引:0,他引:1
Kimble ML Castleman AW Mitrić R Bürgel C Bonacić-Koutecký V 《Journal of the American Chemical Society》2004,126(8):2526-2535
Results for the binding of carbon monoxide and oxygen along with the oxidation of CO in the presence of atomic Au(-) have been obtained utilizing a fast-flow reactor mass spectrometer. In addition, density functional calculations have been performed to explain the experimental findings. It was observed that upon oxygen addition to the metal plasma, gold oxide species of the form AuO(n)(-), where n = 1-3, were produced. The addition of carbon monoxide to the preoxidized gold atom revealed that AuO(-) and AuO(3)(-) promote the oxidation of CO. Density functional calculations on structures and their energetics confirmed the experimental findings and allowed us to propose mechanisms for the oxidation of carbon monoxide. The reactions of CO with AuO(1,3)(-) proceed via complex formation with CO bound to the oxygen atom, followed by either cleavage of the Au-O bond or complex rearrangement to form a weakly bound CO(2) unit, leading in both cases to the emanation of CO(2). 相似文献
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Bürgel C Reilly NM Johnson GE Mitrić R Kimble ML Castleman AW Bonacić-Koutecký V 《Journal of the American Chemical Society》2008,130(5):1694-1698
We present results from our joint experimental and theoretical study of the reactivity of anionic and cationic gold oxide clusters toward CO, focusing on the role of atomic oxygen, different charge states, and mechanisms for oxidation. We show that anionic clusters react by an Eley-Rideal-like mechanism involving the preferential attack of CO on oxygen rather than gold. In contrast, the oxidation of CO on cationic gold oxide clusters can occur by both an Eley-Rideal-like and a Langmuir-Hinshelwood-like mechanism at multiple collision conditions as a result of the high adsorption energy of two CO molecules. This large energy of CO adsorption on cationic gold oxide clusters is the driving force for the CO oxidation. Therefore, in the presence of cationic gold species at high pressures of CO, the oxidation reaction is self-promoting (i.e., the oxidation of one CO molecule is promoted by the binding of a second CO). Our findings provide new insight into the role of charge state in gold-cluster-based nanocatalysis. 相似文献
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CJ Isham 《Contemporary Physics》2013,54(3):207-219
The paper contains a relatively non-technical summary of some recent work by the author and Jeremy Butterfield. The goal is to find a way of assigning meaningful truth values to propositions in quantum theory: something that is not possible in the normal, instrumentalist interpretation. The key mathematical tool is presheaf theory where multi-valued, contextual truth values arise naturally. We show how this can be applied to quantum theory, with the ‘contexts’ chosen to be Boolean subalgebras of the set of all projection operators. 相似文献
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An experimental study of local and global bifurcations in a driven two-well magneto-mechanical oscillator is presented. A detailed picture of the local bifurcation structure of the system is obtained using an automated bifurcation data acquisition system. Basins of attractions for the system are obtained using a new experimental technique: an ensemble of initial conditions is generated by switching between stochastic and deterministic excitation. Using this stochastic interrogation method, we observe the evolution of basins of attraction in the nonlinear oscillator as the forcing amplitude is increased, and find evidence for homoclinic bifurcation before the onset of chaos. Since the entire transient is collected for each initial condition, the same data can be used to obtain pictures of the flow of points in phase space. Using Liouville's Theorem, we obtain damping estimates by calculating the contraction of volumes under the action of the Poincaré map, and show that they are in good agreement with the results of more conventional damping estimation methods. Finally, the stochastic interrogation data is used to estimate transition probability matrices for finite partitions of the Poincaré section. Using these matrices, the evolution of probability densities can be studied. 相似文献
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We report the use of broadband heterodyne spectroscopy to perform continuous measurement of the interaction energy Eint between one atom and a high-finesse optical cavity, during individual transit events of ≈250 μs duration. We achieve a fractional
sensitivity ≈4×10-4/ to variations in Eint/? within a measurement bandwidth that covers 2.5 decades of frequency (1–300 kHz). Our basic procedure is to drop cold cesium
atoms into the cavity from a magnetooptic trap while monitoring the cavity’s complex optical susceptibility with a weak probe
laser. The instantaneous value of the atom–cavity interaction energy, which in turn determines the coupled system’s optical
susceptibility, depends on both the atomic position and (Zeeman) internal state. Measurements over a wide range of atom–cavity
detunings reveal the transition from resonant to dispersive coupling, via the transfer of atom-induced signals from the amplitude
to the phase of light transmitted through the cavity. By suppressing all sources of excess technical noise, we approach a
measurement regime in which the broadband photocurrent may be interpreted as a classical record of conditional quantum evolution
in the sense of recently developed quantum trajectory theories.
Received: 2 June 1998 / Revised version: 4 December 1998 / Published online: 31 March 1999 相似文献
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Dissimilar vertices whose removal leaves isomorphic subgraphs are called pseudosimilar. We construct infinite families of graphs having identity automorphism group, yet every vertex is pseudosimilar to some other vertex. Potential impact on the Reconstruction Conjecture is considered. We also construct, for each n, graphs containing a subset of n vertices which are mutually pseudosimilar. the analogous problem for mutually pseudosimilar edges is introduced. 相似文献