The influence of the resultant momentum on the ion-dipole capture rate in the region of the Su and Chesnavich plateau: A comparison between the statistical adiabatic channel model and transition state theory

Abstract

For some molecular parameters of ion-dipole systems the microcanonical transition state theory (TST), accounting for the conservation of resultant momentum, J , gives simple, analytical equations for the capture rate constants, k 1 ( E, J) and k 1 ( E), and for the boundary values of J max. Previously such values were only obtained numerically. A new interpretation of the adiabatic TST and the numerical integration by the trajectory method (TC) is offered. To calculate the rate constant of the ion-linear dipole capture by using the statistical adiabatic channel model (SACM) in the region of the Su and Chesnavich plateau the best adiabatic potentials, V i ( r), are those obtained by perturbation theory. The capture parameters calculated by SACM, both those that require and those that ignore the conservation of J , do not differ much from those calculated by TST. The difference becomes appreciable at very low temperatures, starting from a temperature 5 times larger than the characteristic rotational temperature. At such temperatures the SACM capture rate constant calculated under the condition of J conservation is equal to the Langevin rate constant, k L.