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Category :
Languages : en
Pages : 12
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Resonantly enhanced multiphoton ionization (REMPI) laser spectroscopic and molecular beam-surface scattering techniques are coupled to study inelastic and reactive gas-surface scattering with state-to-state specificity. Rotational, vibrational, translational and angular distributions have been measured for the inelastic scattering of HCI and N 2 from Au(111). In both cases the scattering is direct-inelastic in nature and exhibits interesting dynamical features such as rotational rainbow scattering. In an effort to elucidate the dynamics of chemical reactions occurring on surfaces we have extended our quantum-resolved scattering studies to include the reactive scattering of a beam of gas phase H-atoms from a chlorinated metal surface M-CI. The nascent rotational and vibrational distributions of the HCI product are determined using REMPI. The thermochemistry for this reaction on Au indicates that the product formation proceeding through chemisorbed H-atoms is slightly endothermic while direct reaction of a has phase H-atom with M-CI is highly exothermic (ca. 50 kcal/mole). Details of the experimental techniques, results and implications regarding the scattering dynamics are discussed. 55 ref., 8 fig.
Author: Michael Scott Westley
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ISBN:
Category :
Languages : en
Pages : 452
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Author:
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Category : Aeronautics
Languages : en
Pages : 1460
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Lists citations with abstracts for aerospace related reports obtained from world wide sources and announces documents that have recently been entered into the NASA Scientific and Technical Information Database.
Author: Jeffrey Tai-Kin Cheung
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ISBN:
Category :
Languages : en
Pages : 248
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Author: Pedro Recio Ibáñez
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Category :
Languages : en
Pages : 277
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Author: Andrew E. Pomerantz
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Category :
Languages : en
Pages : 162
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Author:
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Category :
Languages : en
Pages :
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From proceedings of the International Summer Institute in surface science; Milwaukee, Wisconsin, USA (28 Aug 1973). Molecular beam - surface scattering experiments, the nature of elastic and inelastic scattering, and the information obtained from detection of the angular distribution and kinetic energy of the scattered particles are described. The types of energy exchange that take place between a gas atom or molecule and the surface atoms and the theories that have been developed to explain some of these energy transfer processes are discussed. Finally the results of some experiments are reviewed, and directions for future research are pointed out. (JFP).
Author: Azar Farjamnia
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Category :
Languages : en
Pages :
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The adsorption and dissociation of small molecules on metal surfaces are key steps in many industrial reactions. A detailed understanding of the dynamics of these reactions provides us with the ability to control the outcome and efficacy of the reactions. The molecule-metal interactions will lead to reorientation, energy redistribution, or bond dissociation in the molecule. The process is strongly depending upon the initial conditions, i. e. the incident energy and vibrational state of the molecule, and the surface temperature. We use a fully quantum approach to compute the dissociative sticking probability of the molecules at zero overage, on the surface of metal catalysts. We use density functional theory (DFT) based electronic structure calculations to construct a reaction path Hamiltonian (RPH) for reaction. Using well tested sudden methods for adding the effects of lattice motion into quantum reactive scattering calculations allows us to directly compare the results from our theory with molecular beam studies. Using these methods, we have explored the dissociative chemisorption of H2O, HOD, and D2O on Ni(111), and found that for this late barrier system, excitations in bending and stretching vibrational modes enhance the dissociative sticking. The motion of the lattice atoms near the dissociating molecule was found to modify the height of the barrier, leading to a strong variation in reactivity with surface temperature. We also studied the dissociative chemisorption of CO2 on Ni(100) and the Ni(711) stepped surface. The mechanism for dissociation is similar on the two surfaces, including the formation of a bent anionic chemisorption precursor state. Vibrational excitation of the incident CO2 molecule can enhance the reactivity for low incident energies, and the biggest efficacy corresponds to the bending mode that leads the molecule to the bent precursor state. The vibrationally inelastic scattering of methane molecules from a Ni(111) at low incident energies was studied and we found that the vibrational energy initially in one vibrational state, can distribute into other states upon collision. We have computed this energy distribution using SRP density functional which is a van der Walls correlation functional. At low incident energies the results are similar for PBE and SRP.
Author: Xiaoyan Chang
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ISBN:
Category :
Languages : en
Pages :
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Author: James Alan Schwarz
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Category : Scattering (Physics)
Languages : en
Pages : 388
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