Evidence for two-electron processes in the mutual neutralization of O- with O+ and N+ at Subthermal Collision Energies

TL;DR

This study measures and analyzes the mutual neutralization of O- with O+ and N+ at very low energies, revealing significant two-electron processes and atomic state contributions through experimental and theoretical approaches.

Contribution

It provides detailed experimental cross sections and theoretical modeling showing the importance of two-electron processes in mutual neutralization at subthermal energies.

Findings

Two-electron processes significantly influence mutual neutralization.

Dominant contribution of core-excited nitrogen states in N+ + O- collisions.

Accurate cross sections and state-specific branching ratios at very low energies.

Abstract

We have measured total absolute cross sections for the Mutual Neutralization (MN) of O- with O+/N+. A fine resolution (of about 50 meV) in the kinetic energy spectra of the product neutral atoms allows unique identification of the atomic states participating in the mutual neutralization process. Cross sections and branching ratios have also been calculated down to 1 meV center-of-mass collision energy for these two systems with a multi-channel Landau-Zener model and an asymptotic method for the ionic-covalent coupling matrix elements. The importance of two-electron processes in one-electron transfer is demonstrated by the dominant contribution of a core-excited configuration of the nitrogen atom in N+ + O- collisions. This effect is partially accounted for by introducing configuration mixing in the evaluation of coupling matrix elements.