Electron-impact ionization and ionic fragmentation of O$_{2}$ from threshold to 120 eV energy range

TL;DR

This study investigates electron-impact ionization of O₂ molecules from threshold to 120 eV using a straightforward electron spectroscopy method, providing reliable cross sections and insights into ion formation mechanisms.

Contribution

It introduces a simple, effective experimental setup combining an ion source, collision chamber, and mass spectrometer to accurately measure ionization cross sections of O₂.

Findings

Good agreement with existing experimental and theoretical data.

Highlights the importance of controlling electron-impact energy and pressure.

Provides detailed cross sections for O$^{+}$ ion formation.

Abstract

We study the electron-impact induced ionization of O$_{2}$ from threshold to 120 eV using the electron spectroscopy method. Our approach is simple in concept and embodies the ion source with a collision chamber and a mass spectrometer with a quadruple filter as a selector for the product ions. The combination of these two devices makes it possible to unequivocally collect all energetic fragment ions formed in ionization and dissociative processes and to detect them with known efficiency. The ion source allows to vary and tune the electron-impact ionization energy and the target-gas pressure. We demonstrate that for obtaining reliable results of cross sections for inelastic processes and determining mechanisms for the formation of O$^{+}$($^{4}S,^2{D},^2{P}$) ions, it is crucial to control the electron-impact energy for production of ion and the pressure in the ion source. A comparison of our results with other experimental and theoretical data shows good agreement and proves the validity of our approach.