Energy release repulsive

They have introduced the terms attractive-, mixed-, and repulsive-energy release. These have been defined sharply enough to permit quantitative statements to be made about the nature of a surface. For the reaction A+BC -> AB + C, attractive energy release is the liberation of reaction energy while A is approaching BC, the latter retaining its original bond distance... 

Repulsive energy release is the liberation of reaction energy during the second half of the reaction when C is separating from AB which is in approximately its final state... 

There have been a large number of measurements of angular distributions in desorption which show sharply peaked distributions and these have recently been reviewed by Kislyuk [44]. In some cases the products of reaction on fcc(l 1 0) surfaces are found to be peaked at an angle to the surface normal along the [001] azimuth (Fig. 9) notably for N2 produced by NO [77, 78] or N20 [79] decomposition, C02 formed by CO oxidation [80, 81] and CO formed by C + O recombination [82]. Sharply peaked distributions indicate a repulsive energy release which lies at an angle to the surface normal [83]. This occurs either because reaction takes place on (111) facets on the reconstructed (1x2) missing row surface (e.g., CO formation on Pt(l 1 0)-(l x 2) surface [82]) or, as in the case of N20 decomposition, because the symmetry of the transition state creates a repulsion which is directed away from the surface normal [84, 85]. 

A widely-used model in this class is the direct-interaction with product repulsion (DIPR) model [173—175], which assumes that a generalised force produces a known total impulse between B and C. The final translational energy of the products is determined by the initial orientation of BC, the repulsive energy released into BC and the form of the repulsive force as the products separate. This latter can be obtained from experiment or may be assumed to take some simple form such as an exponential decay with distance. Another method is to calculate this distribution from the quasi-diatomic reflection approximation often used for photodissociation [176]. This is called the DIPR—DIP model ( distributed as in photodissociation ) and has given good agreement for the product translational and rotational energy distributions from the reactions of alkali atoms with methyl iodide. 

An eclectic model has been proposed [280] to describe these dynamics. It includes the separate two-body reactant and product interactions of the optical model with an attractive covalent—ionic interaction between the reactants and a photodissociation-derived repulsion between the products. An impulsive model partitions the repulsive energy release between the product translational and internal modes. There is an abrupt switch between the reactant and product trajectories which occurs for a Cl ... 

An attractive interaction between D+ and A follows the A" B repulsion. The attractive and repulsive energy releases are presumed to be separable, and the attraction is assumed to be slower than the repulsion. 

The opposite limit of direct reaction with repulsive energy release also invites interpretation in terms of simple models. The situation has recently been reviewed by Herschbach134 who shows that the appropriate repulsive potential may be determined from photodissociation spectra of the diatomic reactant in the case of the canonical reactions K + CH3I and H + CI2. 

What would be the opposite situation to the spectator model It would be the case where the final momentum of the C product is predominantly determined by the momentum imparted from the BC bond breaking. An example of this situation would be that of a rebound of A, meaning a purely repulsive reaction. In this case, there is a strong contribution to p from the repulsive energy release of the BC breaking. 

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