Termolecular reactions atomic association

Orbiting, or shape, resonances also play a role in a theory of termolecular recombination developed by Roberts et al. (1969). Their model applies to reactions A + B + M -> AB + M, and assumes that A and B form an excited quasi-bound state, which is de-excited by the third body to form stable AB. Results on H2 + M were compared to those for D2 + M by Roberts and Bernstein (1970). More recently Dickinson et al. (1972) applied the model to ion-atom association in rare gases. 

Until recently, it had not been established whether the association of O atoms with CO was bi- or term olecular. Althou Dixon-Lewis and Linnett [30] and Buckler and Norrish [368] considered their results to be> more consistent with a bimolecular association, Baldwin et al. [395] have pointed out that their interpretation was based on too simple a mechanism for data obtained with KCl coated vessels (see Sect. 10.1.3(6)(iii) and Fig. 68). Shock tube studies definitely indicate that the dissociation is second order at lower pressures, and this implies by microscopic reversibility that the reverse association reaction is termolecular. Kondratiev and Intezarova... 

The suggested mechanism represents a fairly simple chain reaction, wherein the chains are initiated by thermal dissociation of bromine molecules into atoms. The chain-propagating steps involve the conversion of the reactant H2 into HBr by reaction with Br atoms and, since H atoms are produced in the process, the conversion of the reactant Br2 into HBr by reaction with H atoms. The destruction of HBr by H atoms in step 4, which is characterized by 4, accounts for the observed inhibition by the product of the reaction. Finally, the chains are terminated by the termolecular association of Br atoms to form Br2 molecules. 

H atoms, O atoms and OH radicals are the chain centres, and the first two of these reactions each generate two of these centres in return for one. The termolecular association of H with O2 discussed above, forming the comparatively inert HO2 radical, is tantamount to termination. 

Eqn [2]). The reaction of with N atoms is also in- with H2 in a termolecular association reaction pro-volved in NH3 production. Similar sequences lead to ducing thus small hydrocarbon molecules. These sequences of reactions can readily be studied using the selected ion injection facility of the SIFT. 

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