Collision-induced surface reactions

Other means of manipulating ions trapped in the FTMS cell include photodissociation (70-74), surface induced dissociation (75) and electron impact excitation ("EIEIO")(76) reactions. These processes can also be used to obtain structural information, such as isomeric differentiation. In some cases, the information obtained from these processes gives insight into structure beyond that obtained from collision induced dissociation reactions (74). These and other processes can be used in conjunction with FTMS to study gas phase properties of ions, such as gas phase acidities and basicities, electron affinities, bond energies, reactivities, and spectroscopic parameters. Recent reviews (4, 77) have covered many examples of the application of FTMS and ICR, in general, to these types of processes. These processes can also be used to obtain structural information, such as isomeric differentiation. 

J. C. Light and A. Altenberger-Siczek, Laser-collision induced chemical reactions Collinear exchange reaction model on two electronic surfaces, J. Chem. Phys. 70 4108 (1979). 

Surface methyls have also been synthesized by the collision-induced dissociation of methane physisorbed on Ni(lll) surfaces.[7, 8] This approach avoids the effects of coadsorbates other than hydrogen, and a number of aspects of Ae reaction and decomposition of CH3 and CH fragments on Ni(lll) have been determined.[9] However, the method is relatively complex and best suited for study of low coverages. 

Huang and Freiser (132, 133) were able to prepare exohedral metal C60 ions [MC60]+ by direct reaction of the bare metal ions Fe+, Ni+, Co+, Cu+, Rh+, and La+ with Cgo vapor produced from a heated probe. The [MC60]+ ions when subjected to low-energy collision-induced dissociation with argon all produced the Cg0 ion. These results show that the metal ions attach to the outer surface of C60. The exohedral metallofullerene ions differ from the endohedral metallofullerenes produced by laser ablation of metal oxide-graphite mixtures and support the observations of Smalley and co-workers (148) who found that endohedral metallofullerene ions dissociate by loss of C2 units. 

CO2, then the erosion rate might depend on the formation and/or removal rates of these species. A kinetic barrier to the removal of CO and CO2 from the surface would then impede erosion, with the erosion rate being inversely related to the barrier height. If the rate of product removal from the surface is slower than the rate of formation of these products, then the material removal mechanisms, not the reaction mechanisms, could dominate the erosion yield of a polymer. The possibility of collision-induced release of CO or CO2 from an oxidized surface has been investigated in our laboratory, and the results are summarized in this section. 

The F -I- H2 reaction continues to be of interest (75-80). Calculations on F + D2 have been carried out recently on an extremely accurate potential surface (78) and are in remarkably good agreement with crossed beam experiments. Branching between the products in F + HD has been explored (79,80). The F + H2 reaction was recently revisited using an improved surface. Komweitz et al. (82) have probed steric effects in O -I- HC1. Peripheral chemical reactions have also been modeled (83). Collision-induced dissociation in Rg + X2 was recently studied (84). 

The surface-hopping trajectory approach has been applied to reaction and collision-induced dissociation in He + HD (118). 

This book describes the proceedings of a NATO Advanced Research Workshop held at CECAM, Orsay, France in June, 1983. The Workshop concentrated on a critical examination and discussion of the recent developments in the theory of chemical reaction dynamics, with particular emphasis on quantum theories. Several papers focus on exact theories for reactions. Exact calculations on three-dimensional reactions are very hard to perform, but the results are valuable in testing the accuracy of approximate theories which can be applied, with less expense, to a wider variety of reactions. Indeed, critical discussions of the merits and defects of approximate theories, such as sudden, distorted-wave, reduced dimensionality and transition-state methods, form a major part of the book. The theories developed for chemical reactions have found useful extensions into other areas of chemistry and physics. This is illustrated by papers describing topics such as photodissociation, electron-scattering, molecular vibrations and collision-induced dissociation. Furthermore, the important topic of how to treat potential energy surfaces in reaction dynamics calculations is also discussed. 

A Ni metal catalyst was recently used to produce benzene from methane under ultrahigh vacuum conditions(equation 1) by activation of CH4 physisorbed on the Ni catalyst at 47 K by molecular beam techniques at pressures less than lO torr. The selectivity of benzene formation under these conditions is 100% and the reaction proceeds via collision-induced dissociative chemisorptionThe collision of Kr atoms with physisorbed CH4 leads to dissociation into adsorbed H-atoms and methyl radicals the latter dissociate to CH fragments which successively recombine to adsorbed C2H2. Trimerization of C2H2 on the metal surface yields quantitatively C Hg. 

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