Classical-trajectory model for ionizing proton-ammonia molecule collisions: the role of multiple ionization

TL;DR

This paper develops a classical-trajectory Monte Carlo model to study ionization in proton-ammonia collisions, comparing results with experimental data and previous quantum models, highlighting the role of multiple ionization.

Contribution

It introduces a semi-classical CTMC approach with an effective potential for electron dynamics in proton-ammonia collisions, providing a new computational perspective.

Findings

Results are comparable to quantum models at intermediate/high energies.

Double ionization cross sections are larger than experimental data.

Triple ionization cross sections are overestimated by the model.

Abstract

We use an independent electron model with semi-classical approximation to electron dynamics to investigate differential cross sections for electron emission in fast collisions of protons with ammonia molecules. An effective potential model for the electronic orbitals is introduced, and utilized in the context of the classical-trajectory Monte Carlo (CTMC) approach for single-electron dynamics. Cross sections differential in electron emission angle and energy are compared with experimental data. Compared to previous scattering-theory based quantum-mechanical results the time-dependent semi-classical CTMC approach provides results of similar quality for intermediate and high ionized electron energies. We find some discrepancies in the total cross sections for $q$-fold ionization between the present model and independent-atom-model calculations. The double ionization cross sections are considerably larger than recent experimental data which are derived from coincidence counting of charged fragments. The calculated triple ionization cross sections exceed the experimental coincidence data for $q=3$ by several orders of magnitude at intermediate energies.