Kinetic collisions

An electron (or ion) in the gas is accelerated (gains kinetic energy) in the electric field until it collides with a gas molecule (A). In this collision, kinetic energy is transferred to the collision partner and eventually randomized to the rest of the gas. The electron is again accelerated until the next collision, and so on. The average energy attained before each collision is... 

The width of the encounter pair reactivity zone, 672, is to be considered small. There is no reason for this choice, save convenience. Probably rather larger widths would be more appropriate following work on gas-phase collision kinetics or long-range transfer processes (Chap. 4). In such circumstances, the partially reflecting boundary condition is no longer suitable and other techniques have to be used (see Chap. 8 Sect. 2.4 and Chap. 9 Sect. 4). 

In this case no detailed collision kinetics are involved. The collision parameters rnm and the parameters in the Maxwellian post-collision velocity distribution f m are derived from experimentally determined gas viscosity or diffusivity, and the collisional invariants, respectively. Usually this term is negligible in present experiments, but exceptions exist [16]. In particular for ITER, and the high collisionality there, these terms are expected to become more relevant. However, due to the BGK-approximations made, their implementation into the models does not require further discussion here. 

At least two points should be especially emphasized, (i) From the solvent part, the parent radical cations exist in a non polar surrounding. Hence, the cations have practically no solvation shell which makes the electron jump easier in respect to more polar solvents. In a rough approximation the kinetic conditions of FET stand between those of gas phase and liquid state reactions, exhibiting critical properties such as collision kinetics, no solvation shell, relaxed species, etc. (ii) The primary species derived from the donor molecules are two types of radical cations with very different spin and charge distribution. One of the donor radical cations is dissociative, i.e. it dissociates within some femtoseconds, before relaxing to a stable species. The other one is metastable and overcomes to the nanosecond time range. This is the typical behavior needed for (macroscopic) identification of FET ... 

Besides active research he very much enjoys teaching. In the Physical-Technical Institute of Moscow he taught (1966-1992) general courses on Molecular Dynamics and Chemical Kinetics. In the Technion (since 1992) he has taught and still teaches graduate courses on different subjects Advanced Quantum Chemistry, Theory of Molecular Collisions, Kinetic Processes in Gases and Plasma, Theory of Fluctuations, Density Matrix Formalisms in Chemical Physics etc. 

The collision kinetic energy furnishes the potential energy needed to enable the reactants to rearrange to form products... 

Collisions are elastic. This means that, in a collision, kinetic energy is transferred from one particle to another with no overall loss in energy. One particle loses and the other gains an equal amount of kinetic energy. 

Computing the post collision kinetic energy, one finds... 

Solving Equation 6.4 gives the spectrum of bound molecular states with energy Eii = —h kff / 2 x) < 0 and the scattering states ilffCE) with collision kinetic energy... 

The mean free path, A is another fundamental scale necessary for describing the dynamical properties of gases. Mean free path is defined as the average distance traveled by the molecule between two successive collisions. Kinetic theory of gases establishes the following two expressions for the mean free path of gases. 

There have also been many attempts to reduce the likelihood that there will be a collision involving large amounts of kinetic energy. Obviously, if there is no collision, kinetic energy remains potential and therefore benign. Here are a few examples ... 

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