Trajectory calculations of ion–molecule momentum transfer rate constants

Abstract

A classical trajectory method is used to calculate thermal energy momentum transfer rate constants for ions in polar and nonpolar gases. The calculations include the consideration of noncapture scattering. For ions in nonpolar gases, the anisotropy of the polarizability and the ion–quadrupole interaction are also included in the calculations. The results show that the noncapture scattering plays an important role in momentum transfer for ions in both polar and nonpolar neutral gases. For ions in anisotropic nonpolar gases, both the anisotropy of the polarizability and the ion–quadrupole potential are important contributors to the momentum transfer rate constants. The theoretical rate constants are in good agreement with a large collection of experimental results. The theoretical results for polar gases are parametrized to an analytical expression which serves as a useful tool for estimating thermal energy ion–polar molecule momentum transfer rate constants. The present theoretical model is more realistic and provides a more accurate estimation of ion–molecule momentum transfer rate constants than previous theoretical treatments.