Collision effects charge transfer

Charge transfer occurs when particles collide with each other or with a solid wall. For monodispersed dilute suspensions of gas-solid flows, Cheng and Soo (1970) presented a simple model for the charge transfer in a single scattering collision between two elastic particles. They developed an electrostatic theory based on this mechanism, to illustrate the interrelationship between the charging current on a ball probe and the particle mass flux in a dilute gas-solid suspension. This electrostatic ball probe theory was modified to account for the multiple scattering effect in a dense particle suspension [Zhu and Soo, 1992]. 

The internal and external heavy atom effects, IHA and EHA, have attracted a considerable attention in the community of molecular spectroscopists. This is part of an old problem of understanding environmental effects from solvents or solid matrices on S-T absorption or on phosphorescence of solute molecules. For higher temperature studies the triplet decay is quenched either by collision or by vibrational interaction with the matrix or the solvent. The molecules subject to studies in this respect have mostly been aromatic molecules perturbed by molecular oxygen, nitric oxide or other paramagnetic molecules, molecules either with heavy atoms and/or forming charge transfer complexes. 

Gorden and Ausloos have shown that in the presence of additives such as NO or (CH3)2NH, butene becomes an important product, while with no additive or with O2 added, it is not important. The butene probably arises from charge transfer to (CH3)2NH and NO although the latter reaction is endothermic to the extent of 0.1 eV. Stabilization of the butene ion, which in turn leads to butene, was found to be effected by collisions. At higher pressures of ethylene or with added gases such as neon and xenon, the yield of butene was substantially increased. 

Approximate methods such as nonlocal polarizability density models or label-free exchange perturbation theory are useful near the minimum of the interaction potential and go beyond the classical DID model [77]. Several papers deal with effective polarizabilities in liquids [88, 95-98, 140, 152, 391] ionic melts [14, 15, 58] and solids [64, 66, 67, 137-139, 661-663]. The case of charge transfer in atomic collisions has also been considered [71]. 

Our future work on charge transfer collisions will concentrate on fine-structure effects and on polyatomic targets, which present a whole new range of challenges for the type of methodology presented here. 

Watkins has also reported on the solvent effects on the quenching of aromatic hydrocarbons by tetramethylpiperidone jV-oxide. No correlation of quenching efficiency with the charge-transfer properties of the aromatic hydrocarbon free-radical collision complex was found. Other work by Watkins has been concerned with the quenching of aromatic hydrocarbons by stable carbon free radicals. The results are summarized in Table 34. The author proposes that... 

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