Langevin polarization capture

In this relation, r is the distance between the interacting particles, and a is the polarizability of a neutral atom or molecule, which is numerically about the volume of the atom or molecule (see Table 2-4). Typical orbits of relative ion and neutral motion during the polarization scattering are shown in Fig. 2-4. When the impact parameter is high then the orbit is hyperbolic, but when it is low then the scattering leads to the Langevin polarization capture and the formation of an ion-molecular complex. The capture occurs when the... 

The ion-molecular processes start with scattering in a polarization potential, leading to the so-called Langevin capture of a charged particle and formation of an intermediate ion-molecular complex. If a neutral particle itself has no permanent dipole moment, the ion-neutral charge-dipole interaction is due to dipole moment Pm, induced in the neutral particle by the electric field E of an ion ... 

The case of N reaction with various isomers of dichloroethylene is of special interest. With the trans isomer which has no permanent dipole moment the rate coefficient is very dose to the Langevin value (1.810 cm s" ) at all temperatures. For the polar isomers the rate ooeffident is lower than the calculated capture rate but, at 300K, SIFT measurements shows that this is also true for reactions with Moreover the ratio of the experimental value of the rate coeffidents for N and H3 is very close to the ratio of the square roots of the readani... 

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