Reactions of Photochemically Generated Hot Hydrogen Atoms

In general the reaction between two species will have a variety of alternative channels leading to different products, each characterized by a threshold and energy-dependent cross-section. Several products corresponding to these alternative pathways are observed in experiments with nuclear recoil atoms, whereas thermal 

Hydrogen atoms with translational energies above and below the threshold for reaction (1) are shown as H and H, respectively, and M refers to any added inert molecule which removes energy from in modo ating collisions. St (1) and (3) represent reactions occurring at all energies between the initial value with which the atoms are produced and the threshold, and (2), (4), and (5) are multistage thermalization processes. Most of the thermalized atoms are removed by reaction (6). Thus the ratio of Hi to HD in the products at low conversion is 

It can be seen from (8) that the addition of moderator decreases the yield of hot reaction product HD, which is a useful diagnostic test for hot reactions. The coefficients ki—ks are averages over the distribution of hydrogen atom energies within the system, and therefore vary with the initial energy of the atoms. Relationships between product and reactant ratios of the type indicated by (8) have frequently been observed and are characteristic of hot reactions  

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Reactions of Photochemically Generated Hot Hydrogen Atoms H + CH3CH=CHj -> CH3CH2CH CH3CH2CH CHj + C3H4... 

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