Classical-trajectory time-dependent mean-field theory for ion-molecule collision problems

TL;DR

This paper introduces a classical-trajectory mean-field model for ion-molecule collisions, incorporating molecular structure and dynamical screening, and applies it to water and ammonia, comparing results with experimental data.

Contribution

The work develops a classical-trajectory mean-field approach with dynamic screening for ion-molecule collisions, advancing the modeling of electron transfer processes at the classical level.

Findings

Successfully models electron transfer in water and ammonia collisions.

Provides differential and total cross sections consistent with experimental data.

Highlights the strengths and limitations of the classical-trajectory mean-field method.

Abstract

A mean-field model to describe electron transfer processes in ion-molecule collisions at the $\hbar =0$ level is presented and applied to collisions involving water and ammonia molecules. Multicenter model potentials account for the molecular structure and geometry. They include charge screening parameters which in the most advanced version of the model depend on the instantaneous degree of ionization so that dynamical screening effects are taken into account. The work is implemented using the classical-trajectory Monte Carlo method, i.e., Hamilton's equations are solved for classical statistical ensembles that represent the initially populated orbitals. The time-evolved trajectories are sorted into ionizing and electron capture events, and a multinomial analysis of the ensuing single-particle probabilities is employed to calculate differential and total cross sections for processes that involve single- and multiple-electron transitions. Comparison is made with experimental data and some previously reported calculations to shed light on the capabilities and limitations of the approach.